Tag Archives: Oracle BI Suite EE
Performance and OBIEE – part II – Test – Define
Take the first tentative steps along the yellow brick road of investigating performance and OBIEE with this jump into the nitty gritty of how we should define a performance test.
An overview of defining a performance test
The first step in assessing the performance of OBIEE is defining the test we are going to use. For troubleshooting a performance problem in Production, this might be a single report. For performance testing a new system it might be more complex. The process to define it needs to be the same though.
Let us consider for a moment what it is we want to achieve through a performance test. It should be a validation – or possibly determination – of some or all of the following, which may or may not be formally documented in a project as ‘Non-Functional Requirements’ (NFRs):
- Report response times
- User concurrency levels
- Hardware utilisation
It doesn’t sound too difficult does it? We can run a report and time how long it takes, and we can run the same report multiple times in parallel and see how long it takes then, and around all of that we can gather system OS stats.
This seems to be the level at which some people perceive the complexity of performance testing; that is, not at all.
But, to put any weight in the above results would presume that the system under test had :
- Only one report
- No parameters or other interactivity on the report
- Every user runs the report at the exact same time
How many OBIEE implementations do you know that match this description?
As soon as you accept this premise, then you have to accept the need to design your performance test properly if you want any kind of confidence in the results that you get.
Of course, there is the chance – [sarcasm]vastly improbable and unheard of I know[/sarcasm] – that Performance Testing is a tick box on a project plan (normally about a week before Go Live), from which there is the expectation that it can deliver the confidence of an accurate test with the simplicity and brevity of the one-report test I describe above. If that is the case then I hope this article will explain why it is a fallacy.
Walk before you run
There are three key things to aim for in the design of a performance test:
- Repeatability. You must be able to rerun the test, so that you can (a) prove bugs/performance problems have been fixed, and (b) re-use the test as a baseline for future measurements
- Accuracy. This can be difficult with a stack as complex as the OBIEE one, but you must do all you can to avoid conflation and misinterpretation of data.
- Ease of Analysis. If the result of your test is unsuccessful, you will have to start analysing the issue. If your test is unnecessarily big or complex then it will be very difficult and time consuming to pare it back to find root cause.
Avoid the blunderbus approach. It’s tempting (and fun!) to get carried away building a huge test and run it with a big number of users – but if it brings the system down then the only immediately conclusion you can draw is that you can crash the system. To get to any kind of root cause of the limitation you will have to run more tests, and you will have to simplify the test that you did run to pinpoint the actual issue(s).
Build up small tests with single users and check things work at this level first. You can then combine these together into larger tests for load testing. By working this way you get the added benefit of a better understanding of the workings of your load test and system being tested, as you will have gained this experience from the smaller tests.
Think of it as assembling a car’s engine for yourself versus buying a car out of the showroom. If it breaks (or you want to tune it), you’ll be in a better place to start if you have been under the bonnet [hood] already.
Define a User
The first step in defining a good test is to define extremely precisely and clearly what it is we are testing. This section’s heading I take from Zed Shaw’s superb article “Programmers need to learn statistics…”. For me it encapsulates in three words the challenge that we face in designing a good test. We know we want our system to support more than one user, and we probably have a user concurrency figure (of which more below) that the system must support. So, how do we define ‘a user’? To quote from the aforementioned article, do we just “click around a bit, you know, like a user”? Maybe we run the OBIEE-equivilent of SELECT 1 FROM DUAL
a thousand times simultaneously, and then declare our system can support a thousand concurrent users?
The challenge is that good test or not, test results and system capacity will often be boiled down to a discussion of simple “user” numbers. Will the system support 100 users? 200 users? And so on.
Modelling the workload of a transactional (OLTP) system is relatively straightforward in that there is a finite number of transactions, even if it is a large number. When we consider how to model an OBIEE user in a performance test, we have additional challenges:
- Navigation paths
- In an OLTP system such as an online store once a user clicks on ‘add to cart’ we can be pretty sure they will then either (a) carry on shopping or (b) go to checkout. What about a BI user once they’ve run their first report, which will they run then? Maybe a different report, but quite likely it will be navigation within the existing report (eg drill down, prompt changes, etc)
- Ad hoc
- Whilst some reporting will be fixed reports, much business value from BI comes in the analysis and exploration of data in an ad hoc manner to discover trends etc to give competitive advantage. These ad hoc queries cannot, by definition, be known in advance, so the performance test definition must find a way to address this.
Think about how many types of users you have on your system, and how you would characterise and group them. There will be different sets of data they access, and varying degrees of interactivity with which they use the tool. Some will be using pre-built reports with fixed filters, other may be doing extensive ad-hoc analyses, and somewhere in the middle will be pre-built reports but with a fair amount of interactivity through functionality such as prompts and selection steps.
Define a Report
So for each of our User types that we define, we need to precisely define the workload for them. This will be made up of the execution of one or more dashboards/reports. Defining the report that our model users are going to run is not as simple as it may appear. As well as the distinction to make between individual reports (Analyses/Answers) and Dashboards, we also need to consider:
- Filters
- How do we model a report which has six possible filters? We can’t just call that ‘report A’, because each filter permutation could cause different SQL to be generated by the BI reporting tool and consequently vastly different execution plan(s) on the database where the query runs.
- Aggregate navigation
- One of OBIEE’s many strengths is its aggregate navigation capability, enabling the user to drill down into data whilst in the background the tool switches between pre-defined aggregate tables on the database to pick the fastest one to use. For performance testing we need to make sure that within a report each possible aggregate is considered separately.
As an example, let us examine a dashboard from SampleApp.
At an initial glance, we could specify our “Report” as simply being “Dashboard 3.10”. But…the dashboard is made up of three analyses (plus some static text/image objects)
- “Product Line Analysis”
- “Ragged Hierarchy”
- “Value Based (Parent Child) Hierarchy”
We need to consider each of these reports individually. In addition, there are hierarchical columns which, like Prompts, must be included in our test specification. Here’s one of the reports from the dashboard in two different states of hierarchical navigation.
The first version, mostly collapsed, requires 3 queries against the database. The second version requires 21 queries! Clearly the performance of the two different versions of the report is going to differ.
Depending on the hierarchical column states, depending on dashboard prompt values, depending on aggregate drill paths followed, the same individual report has the potential to behave quite differently.
Any report or dashboard that’s using prompts needs to have those prompt values stated in the test definition. The execution of a query on the database can vary considerably depending on the predicates supplied, and it is in part from the report/dashboard prompts that these predicates come.
Ad-hoc reports
Conspicuous by its absence from the above is how we deal with ad-hoc reporting with OBIEE in our performance tests. This is the elephant in the room when it comes to performance testing OBIEE, because we cannot go through the same methodical process of cataloging the workload – because it is ad hoc. This is discussed in detail later.
User workload
Having precisely defined the reports which are going to be run, we can sequence them together to represent different types of users. Clearly this is going to be a generalisation, an estimation, of how a particular group of users is going to tend to use the reports. Unlike an OLTP transaction, where the steps are much more predefined and free from possible deviations, users of OBIEE have the flexibility to run any number of reports, drill within existing reports, and so on.
Taking the above SampleApp dashboard as an example, one user (let’s call them the “Product Analyst”) might have the following test sequence:
- View
Dashboard 3.10
in default state - Drill into hierarchical columns of
Product Line Analysis
- View
1.3 Sample Sales - Product Details
Some user types may just run one report and exit; they don’t have to have a complex sequence.
You don’t need to restrict yourself to one user type per actual group of users. You could model several different instances of each user group in order or increase the test coverage and realism of different reports running concurrently. Be aware that the more user types and tests you have, the longer it will take to build, and the more complex the troubleshooting could be.
Think Time
Users are not computers, which is a shame because it would make reasoning with them a lot easier. It also means that they do not just one run report after another. They run a report, look at the numbers, get a cup of tea, change a prompt value, have a chat with a colleague, and so on.
As part of your user workload, plan in some think times. Don’t spend too long thinking about it (geddit), because remember this user workload is an approximation of what a certain type of user is going to be doing.
User concurrency
Once we have designed a set of individual user workloads, we can bring these together into a larger test to assess the performance of the system as a whole under load. The aim of load testing is to assess what happens to the response time of reports, and hardware utilisation, as the number of concurrent users on the system increases. There are three key things to define in a load test:
- the workload of each user
- the different types of user
- the number of concurrent users
The first two of these are discussed above. When it comes to user concurrency, we need to be very careful how we derive our figure, because it has a big impact on the scale of the tests that we run and the discussion of the outcomes.
First, make sure that you are clear in the definition of concurrency that you use. These include:
- Concurrent user sessions logged into OBIEE, viewing dashboards, formatting reports, and so on.
- Concurrently executing queries at the BI Server level, which could be a single user running one report or one dashboard.
- Concurrently executing queries on the database, which could be a single user in OBIEE running a single report or dashboard requiring more than one SQL request to get its data.
Each of these have their own particular load on the system, but can easily differ by orders of magnitude. Typically a user concurrency figure will be derived from “bums on seats”, i.e. number of users. From this, a reckoning is made on how many will be using the system at one time. So unless it’s qualified otherwise, I would work with the first definition – concurrent user sessions logged into OBIEE. But if this is your definition, remember it when we come to simulating users later on …
For some reason, user concurrency is often a contentious number to define. With the greatest of apologies to Monty Python, I offer this paraphasing of a familiar conversation:
“yah, my system needs to support 100 concurrent users”
“100? I’d take that as a QUIET DAY for my system, bwahaha, I need to test at least 1,000 concurrent users!”
“1,000? You were LUCKY! My system would run a gazillion concurrent users at three o’clock in the morning, work twenty hours down t’pit and still run 5,000 concurrent users before having a handful of cold gravel for its tea”
There does seem to be BSD syndrome around user concurrency figures, with people always pitching high numbers. This is counterproductive. If you run a performance test using a completely simulated workload with an excessively high number of users as the target then the margin of ‘error’ (how accurately your test represents reality) inherent in the simulation approach will be magnified as the user concurrency increases. The net effect of this is that you cannot be confident that any problems that do happen will actually happen in real life. Conversly, if you are taking real workload and running it for many users, you can honestly say if it doesn’t work in testing, it won’t work in real life.
If you are worried about pitching your user estimate too low and so double it or stick a zero on the end just in case, consider the following: If you define your test as being a fail if it does not support your high figure of concurrent users – what then? You have to ask for money, either literally to buy bigger hardware, or in kind, to support the time to optimise the system you do have. It’s not a great place to be in, and one which may be unnecessary. A sensible approach is the following:
- Load test to confirm whether the system can support the realistic number of users in the short-term, e.g. go-live and a few months beyond
- Defer part of the load testing until after go-live, when you can run a test for medium/long-term user numbers using real user workload for your tests. The benefit of this is that your second test will be far more accurate because your simulation will not be based on how you think you system will be used but how you know is it being used.
If this approach doesn’t suit, then your alternative should be to
- take a realistic figure to start with for your first test
- run a second performance test to validate a future growth figure for your user base. If you don’t have a future growth figure, then you could consider the second test being to simply determine how many users your system can support by ramping numbers up until things start to creak.
The point of doing it this way is that the first test – assuming it gives a positive result – gives clarity and focus to your overall results. If the second test fails, then at least you have the confidence from the first with which to proceed with a decision. If you just run one big test then it’s an “all or nothing” approach, and if the test fails you have the option of either delaying launch until a successful test, or just crossing your fingers and hoping.
User concurrency numbers for an existing system
If you have an existing system then it is easy to determine your actual user concurrency through either Usage Tracking (you do have it enabled, don’t you?) or the OBI DMS metrics.
- If your user concurrency figure is based on users logged into OBIEE, not necessarily running reports, then the metric Oracle BI PS Sessions : Sessions Logged In should be appropriate.
- For the number of queries (logical SQL) concurrently running on the BI Server, use Usage Tracking (see below), or DMS metric t.b.c!
- The number of concurrent queries on the database can either be obtained from your database’s monitoring tool, or through the Oracle BI DB Connection Pool DMS metrics.
To find out more about viewing and capturing OBI metrics over time, see here.
To estimate user concurrency from Usage Tracking, you can use the following query. It will analyse Usage Tracking to give an approximate number of concurrent users, but this is based on individual queries run on the BI Server, so it not the same as users simply logged into OBIEE, nor the same as dashboard refreshes (since one dashboard could be many queries):
-- Usage Tracking Concurrency usage estimate
-- Per minute granularity
SELECT TO_CHAR(start_ts, 'YYYY-MM-DD HH24:MI') AS start_ts_min,
COUNT(DISTINCT user_name) AS distinct_users
FROM s_nq_acct
GROUP BY TO_CHAR(start_ts, 'YYYY-MM-DD HH24:MI')
ORDER BY 1 DESC
Estimating user concurrency numbers
If you don’t have empirical numbers to use then 10% of your total user base is the rule of thumb often worked to.
User concurrency is multi dimensional
Just as there is no such thing as “A User”, to ensure an accurate performance test user concurrency figures should also be specified in terms of :
- Types of concurrent user, for example:
- “10 Concurrent Finance Power Users”
- “2 Concurrent Finance Ad-Hoc Users”
- “60 Concurrent HR Report Consumers”
- Periods of system usage, for example:
- Monday morning peak
- EOD peak
- ‘Average’
You may only actually test the peak user concurrency model, but it’s a good idea to have a picture of the system profile, particularly when analysing the impact and capacity for ad-hoc usage.
Summary : User and Report Definition
Remember:
Before you can measure something you really need to lay down a very concrete definition of what you’re measuring. – Zed Shaw
Whatever kind of testing you are doing, aim to make it modular wherever possible. It will make both analysis and reuse of test code easier.
Almost all test definitions should be made up of one or more of the following levels:
- Specific Report or dashboard along with all prompt values, hierarchical column settings, etc. This is the base unit of your performance test.
- Then take these individual tests, and use them together to create an individual User Workload model for each user.
- Finally, combine the User models to produce an overall Concurrent User workload simulation.
See below for a worked example of a sample test definition.
Points to remember in your test definition:
- Whilst each dashboard does have its own name, a good idea is to use your own ID system to make it easy to refer to a specific dashboard state. For example, when using prompts there might be two or more versions of the dashboard to test (for different prompt values).
It’s also easier to refer to something like “ID01” in conversation and notes than it is it “Finance Dashboard – Profitability EMEA blah blah blah”. - Don’t forget default values in your navigation. If you are testing specific dashboard prompt values, you’ll need to also test the default values first – because that is what will get executed when the user first clicks onto the dashboard.
- As well as testing dashboard response times, factor in the usability of any prompts that the user will interact with. A fast dashboard is not quite so impressive if the user had to wait a long time for the dashboard prompts to display the available values.
- You need to be writing down nuts and bolts detail here. Resist the temptation to skimp on the detail or assume you’ll remember – you won’t, and certainly your colleague who can reuse your testing won’t appreciate having to fill in the blanks to make use of it.
What do you mean, not all of it has been tested?
Before you run off to write down all your dashboards and types of user, consider the following. Unless you have :
- A very small system
- A lot of time, and/or an infinite number of monkeys
you are not going to be able to actually test all of your OBIEE system. Fact.
There are too many factors (prompt values, aggregate paths, ad hoc usage) to be able to model all plausible (let alone possible) permutations of these.
Designing the scope of a performance test needs to take into account the acceptable risk of things going wrong vs time/budget available vs functionality required. By functionality, I mean factors such as the breadth of dashboards delivered, or data made available.
- In some systems the stability is paramount and therefore the relative risk must be minimised. If this is the case and your time/budget is constrained then therefore the functionality will have to be constrained.
- If you need to deliver a lot of functionality and assuming that time/budget is fixed, then you will need to accept an increased risk to the stability of your system.
- If you have limitless time/budget then you can deliver lots of functionality and do large and wide-ranging performance tests to ensure minimal risk.
The point here is an important one because it is one that needs discussing with the project owner, or more specifically, whoever will be accountable if things don’t go right in Production. For a standard OLTP system it is much easier (relatively) to design a performance test with a high degree of confidence that most [common] workloads have been simulated and tested. However, for a reporting system such as OBIEE there are two reasons why it isn’t so easily determined, as discussed above and re-iterated here:
- Permutations of fixed reporting – each dashboard can have multiple prompt dimensions, hierarchical column expansions. Users can follow many different drill and navigation paths from any one dashboard.
- Ad hoc reporting – by definition, the report is not known until the user builds it, so we cannot test it beforehand
But, all is not lost. Even if we accept that to test every permutation of report that might run is impossible, it is still perfectly realistic to perform a thorough performance assessment of a system prior to go-live. The most sensible option is a hybrid approach of:
- Traditional performance testing of fixed reports as described above
- Testing predefined ad-hoc reports (if that isn’t a paradox)
- Holistic and heuristic evaluation of the system design and data model
- Resource management to curtail the impact of bad queries
- Active monitoring to identify bad queries and deal with them (using the T.E.A. method)
- Feedback loop : as system usage becomes clearer, refine original performance testing using a more accurately informed model (using the T.E.A. method)
This may seem a bit of an excuse for a cop-out. If we can’t performance test all our system and be confident in the results, what’s the point? Here, I defer to Cary Millsap, a great proponent of the rigorous, scientific, and rational approach to performance testing:
How can you possibly test a new application enough to be confident that you’re not going to wreck your production implementation with performance problems?
You can model. And you can test. However, nothing you do will be perfect. It is extremely difficult to create models and tests in which you’ll foresee all your production problems in advance of actually encountering those problems in production.
Some people allow the apparent futility of this observation to justify not testing at all. Don’t get trapped in that mentality. The following points are certain:
- You’ll catch a lot more problems if you try to catch them prior to production than if you don’t even try.
- You’ll never catch all your problems in pre-production testing. That’s why you need a reliable and efficient method for solving the problems that leak through your pre-production testing processes.
Somewhere in the middle between “no testing” and “complete production emulation” is the right amount of testing. The right amount of testing for aircraft manufacturers is probably more than the right amount of testing for companies that sell baseball caps. But don’t skip performance testing altogether. At the very least, your performance test plan will make you a more competent diagnostician (and clearer thinker) when it comes time to fix the performance problems that will inevitably occur during production operation.
An example OBIEE test definition
Here’s an example test definition, put together from SampleAppv207.
What we are going to model is two groups of users. One likes pretty pictures and just runs two chart-based dashboards and then logs out. The other is interested in numbers and does some filtering on an analysis dashboard.
First, we’ll define the dashboards in use. For brevity, I’ve omitted the constituent analysis details, but in normal practice it’s a good idea to include them (for future reference, ease of understanding, clarity, etc).
Dashboards
Dashboard : ID01
- Dashboard : 3.20 Vanilla Visuals
- Page : Standard Visuals
- Path :
/shared/3. Analysis and Dashboards/_portal/3.20 Vanilla Visuals
- Dashboard Prompts: None
- Analyses :
/shared/3. Analysis and Dashboards/Report Views/Gallery/Examples of Standard Visualizations
Dashboard : ID02
- Dashboard : 3.20 Vanilla Visuals
- Page : Trellis-Product Sales
- Path :
/shared/3. Analysis and Dashboards/_portal/3.20 Vanilla Visuals Trellis-Product Sales
- Dashboard Prompts: None
- Drill state : Default (NB each chart can be clicked on to drill into detail)
- Analyses :
- /shared/3. Analysis and Dashboards/Report Views/Trellis/Revenue Breakup
- /shared/3. Analysis and Dashboards/Report Views/Trellis/Product Cost and Unit Price Trend
- /shared/3. Analysis and Dashboards/Report Views/Trellis/Brand Cost and Unit Price Trend
- Offices Region Hier : All collapsed, except AMERICAS expanded one level
Dashboard : ID03
- Dashboard : 1.3 Sample Sales
- Page : Brand Analysis
- Path :
/shared/1. Quick Demos/_portal/1.3 Sample Sales Brand Analysis
- Dashboard Prompts:
- T05 Per Name Year : Default (2008, 2009, 2010, 2011)
- D4 Company : Default (none)
- T31 Cal Week : Default (between 0 and 53)
- “Products”.“Products Hierarchy” : Default (none)
- Analyses :
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Product Line Analysis
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Trending Analysis
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Gauges
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Top Customers Bookings
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Daily Revenue Timeline
Dashboard : ID04
- Dashboard : 1.3 Sample Sales
- Page : Brand Analysis
- Path :
/shared/1. Quick Demos/_portal/1.3 Sample Sales Brand Analysis
- Dashboard Prompts:
- T05 Per Name Year : 2010, 2011
- D4 Company : Stockplus Inc.
- T31 Cal Week : between 1 and 27
- “Products”.“Products Hierarchy” : Default (none)
- Analyses :
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Product Line Analysis
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Trending Analysis
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Gauges
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Top Customers Bookings
/shared/1. Quick Demos/Simple Demo Dashboard/Brand Analysis/Daily Revenue Timeline
Tip: Use Catalog Manager to generate a report of dashboards and their constituent analyses to make the creation of the above specification easier. :
User Workload
Having defined the dashboards (ID01 – ID04), we define the user types and workloads:
User A
- Description: Department X, executive
- Workload model:
- ID01
- Think time: 60 seconds
- ID02
- Think time: 60 seconds
- Logout
User B
- Description: Department Y, analyst
- Workload model:
- ID03
- Think time: 120 seconds
- ID04
- Think time: 90 seconds
- Logout
Concurrency
Our concurrent user model looks like this. I am defining concurrent users as active users, that is, executing dashboards or simulated thinking.
Peak usage
- User A : 5 concurrent users
- User B : 2 concurrent users
Light usage
- User A : 3 concurrent users
- User B : 1 concurrent users
Types of testing
Before we can consider the types of test, we need to define what it is we are testing, hence the long section above. Once you’ve identified the types of user and specific reports they will run, you should also look at the type of test you want to run. The terminology is frequently used interchangably, so here’s my version of it:
- Performance testing
- With a single user, is the response time acceptable?
- Load testing
- With concurrent users, is the response time acceptable and stable?
- Capacity testing
- How does the system behave when concurrent users are simulated? do any areas show signs of reaching capacity of resource?
- Soak testing
- How does the system behave if the concurrent user workload is left to run for many hours? For example, are there any memory leaks lurking, or connections which are not closed down properly and will eventually run out?
- Stress testing
- As we increase the number of concurrent users beyond that required (and already tested successfully), how far will the system go until something breaks or response times suffer?
- In a high-availability deployment, what happens to response times if we simulate partial stack failures? Does the system handle this gracefully under load?
These types of test do not have to be mututally exclusive in execution, but in defining your testing make sure you have covered them all, or explained why they are not necessary. An example would be performance testing a single report change on an existing system would probably not warrant a full scale soak test.
In summary
The output of this phase of the method should typically be a set of test definitions, not one single one. As already discussed, keeping tests modular and simple is a much better approach than trying to kill all the birds with one boulder.
Footnote: The soft squidgy side of performance testing
Tangent: Enterprise change control processes
Taking the premise discussed above – that it is impossible to test every possible report execution – raises an interesting question around change control and the stability of a Production environment. If your company is one where releases must be triple tested and signed off in the blood of your firstborn the you might want to have this conversation sooner rather than later. Why? Well if your system has any element of ad-hoc usage then there is a chance that a user will run a query that disrupts other users on the system. There is always the potential for the perfect storm of it being a critical business period, high user traffic, and a rogue ad-hoc query. Without proper understanding of the nature of ad-hoc queries, an almighty witch hunt can ensue, looking for who broke Production.
If this kind of risk is unacceptable then you will have to look into mitigating it with things like resource management and environment partitioning.
Estimating performance test for project planning
The challenge that the complexity and multiple facets of performance testing gives is finding a way to communicate it accurately to project managers and business sponsors.
Unlike an estimate for code delivery, which will be <x> days and after which the code will either function or not, performance testing can pretty much take as long as you like, and the kicker is that the tests will only give varying degrees of confidence that things should be OK in production, but with no guarantees.
Doing the initial analysis on the system is a fixed time, as is building the test rig(s) with which to test it. Once you have done this, then defining the number of dashboards to test can be done based on the time available. The more dashboards are tested, the greater certainty can be had that any problems will be uncovered. Other fixed tasks should be a review of the overall design, as well as time to properly document the tests undertaken and an analysis of the results obtained. It is a false economy to skimp on the documentation, as to do so renders almost useless the results obtained for future work. Good documentation of testing undertaken and results found can greatly shorten the time necessary in the future when revisiting the work either for a new phase of development or to troubleshoot performance problems that have arisen.
What next?
Next up is designing the test that we’ve just defined … read on!
Other articles in this series
This article is part of a series on the subject of Performance and OBIEE:
Comments?
I’d love your feedback. Do you agree with this method, or is it a waste of time? What have I overlooked or overemphasised? Am I flogging a dead horse?
Because there are several articles in this series, and I’d like to keep the discussion in one place, I’ve enabled comments on the summary and FAQ post here, and disabled comments on the others.
Does the BI Server System Component Make Full Use of My Multi-Socket, Multi-Core Server?
An interesting question came up during a client visit the other week, where their system had some performance issues and I was asked to take a look at it for them. One of their concerns was whether OBIEE 11g, in particular the BI Server system component within it, was making full use of the CPUs and cores on their server – in particular, they’d noticed just one or two CPUs at near 100% utilisation when certain queries were running, even though there were many, many more CPUs available that the BI Server could use. What was going on, and was there an in-built limitation with the BI Server where it serialised everything through a single CPU when many more were sitting idle?
Thinking the answer through, it’s quite an interesting topic and there’s actually several aspects to how the BI Server works in a multi-socket, multi-core environment. To take an example; consider a situation where OBIEE 11g is running on a server that’s got four sockets, each with four cores in it, for a total of sixteen cores. Most modern OSs will consider this as sixteen CPUs, which the processor count that the Oracle database, OBIEE and other applications will consider as available.
These CPUs also generally support something called multi-threading; threads are sequences of operations owned by a process (such as nqsserver, the BI Server OS executable) that an operating system executes via a scheduler and some sort of time-sharing/multi-plexing arrangement, depending on the OS and hardware. All applications and services that run on a server that uses these features will benefit from multi-threading in that they can appear to run at the same time as other applications, but those that benefit the most are ones that themselves internally support multi-threading, and can therefore initiate several tasks at once – and one such application is the BI Server system component.
What this means in practice is that when the BI Server component starts up, it creates and reserves a number of threads in advance, determined by a number of parameters including SERVER_THREAD_RANGE. As queries come in from the BI Presentation Server, the BI Server component uses these threads to issue queries to the underlying source database, manage client connections, communicate with database servers and so forth. You can see these threads running and ready to perform tasks for the BI Server component by using a tool such as Process Explorer for Windows; in the screenshot below, you can see the single BI Server process (nqsserver.exe) running as a child process of opmn.exe, the Oracle Process Manager and Notification Server that manages OBIEE’s legacy non-Java components.
Double-clicking on that process shows you the threads associated with it; in this case, even for a largely unused system there are over a hundred threads open, ready to handle queries and perform other management and communication tasks.
So going back to the original questions; for a given end-user query, will the BI Server execute everything on a single CPU, or will it make use of all of the CPUs on the server? Well, given that the BI Server is multi-threaded, what this question is really asking is whether all of the BI Server’s threads run on a single CPU, or whether all of the threads associated with a given query run on a single CPU, effectively ignoring much of the CPU capacity on the server.
Thinking it through a bit, any given single query is, to a certain extent, only really going to use a small part of the total amount of CPUs available on a server, because it’s not the BI Server that runs queries in parallel, it’s the underlying database. For example, a single analysis against a single Oracle Database datasource would only really need a single BI Server thread to handle the query request, but when the underlying database receives the query, it might use a large number of its CPUs to process the query, returning results back to the BI Server to then pass back to the Presentation Server for display to the user. The BI Server wouldn’t have any use for any more query threads, as it can’t really do anything with them – the exception to this being queries that generate multiple physical SQLs, for example to join data from multiple sources together and return a single set of data to the user, for which the BI Server could benefit from a higher CPU count if each of these queries in turn led to lots of threads being used – but two queries, in themselves, don’t neccessarily require two CPUs, because of course the BI Server, and the underlying CPUs, are themselves multi-threaded.
So let’s go back to Windows and see what happens when individual queries come in. The Threads view in Process Explorer actually displays, for each thread, the CPU (processor) that it is most likely to next run on, as you can see from the screenshot below:
Looking at the threads at the top of the list (those that have run most recently), see how the Ideal Processor value is now 6 – this this an eight-processor Windows Server 2008 64-bit server it’s running on.
So why does it use the term Ideal Processor, rather than just Processor? In fact, which CPU a thread runs on (or, technically, is scheduled to run on) is actually determined by the OS and is effectively “abstracted” away from individual processes, as long as are designed for multi-threading and don’t have any serialised single-threaded limitations. This is how the BI Server is written, with no explicit code to spread threads over more than one CPU, but with the OS doing this for it instead based on a number of factors. It’s also where there’s that annoyingly vague set of guidelines around whether it’s best to vertically-scale the BI Server component on a multi-processor 64-bit system – some OSs and hardware platforms might, in the background, limit processes to a subset of the available CPUs, some might not, so therefore the vague guidelines that it “might” be worth adding more BI Server components into an Oracle Instance, just as it “might” make better use of overall memory – you’ll have to try it on your own system and see.
To conclude then – all things begin equal, the BI Server should make use of all of the CPUs that the underlying operating system presents to it, with the OS itself deciding what threads are scheduled against which CPUs. In-theory, all CPUs on the server are available to each BI Server component, but each OS is different and it might be worth experimenting if you’re sure that certain CPUs aren’t being used – but this is most probably unlikely and the main reason you’d really consider vertical scale-out of BI Server components is for fault-tolerance, or if you’re using a 32-bit OS and each process can only see a subset of the total overall memory. And, bear in mind that however many CPUs the BI Server has available to it, for queries that send just a single SQL statement down to the underlying database server, adding more CPUs or faster CPUs isn’t going to help as only a single (or so) thread will be needed to send the query from the BI Server to the database, and it’s the database that’s doing all of the work – all that this would help with is compilation and post-aggregation work, and enabling the server to handle a higher number of concurrent users. Invest in a better underlying database instead, sort out your data model, and make sure your data source back-end is as optimised as possible.
Report Flexibility, or Split-Second Performance : Pick One or the Other
Kevin McGinley wrote an interesting post the other week reflecting on Oracle Endeca Information Discovery (OEID), and the role that it’s come to play within Oracle’s BI tools strategy. Kevin’s view was that whilst Oracle positioned OEID originally as an “unstructured data”, or even “big data” tool, where it’s got the most take-up in Kevin’s view was around fast, ad-hoc analysis with minimal up-front data modelling, something that traditionally OBIEE has been a bit weak at. I was reminded of Kevin’s post last week whilst on-site with a customer’s IT department, who were struggling with that age-old problem: how do we provide a reporting system to our users that puts no restriction on what they can do, but that also returns the results of all queries within seconds. Why is this so hard then?
OBIEE, and most of the rest of the “enterprise” BI platforms in my experience, are typically selected and then implemented by the IT department, because it ticks lots of boxes around integration with ERP systems, corporate middleware and security, and they can usually get a good deal license-wise if it’s part of a wider EBS upgrade, for example. IT departments then sell OBIEE to the business as offering flexibility and self-service reporting, all without having to involve the IT department when you need a new report creating. Which is true of course, but there’s also the pleasant side-effect for IT in that users are, in fact, quite severely constrained on the data they can use in their reports, and the way in which they can combine it, and it usually does involve IT when changes to the RPD are made, for example to bring in a new data source or add a new hierarchy.
The reason for which, of course, is because the types of dataset typically reported against by OBIEE – large data warehouses, federated data marts, even transactional databases – will typically return results very slowly to users unless they’ve been indexed, summarised and otherwise optimized by the DBAs beforehand. Some of this is just basic physics – relational databases and disk-based storage is optimized for storing lots of data, in-detail, very safely, but you can’t just throw any query at it and expect it to consistently return results in a split-second – not unless you bake-in some fairly constrained access paths, pre-compute and summarise in advance, or even use technologies such as Oracle Exalytics and TimesTen to replicate “hot spots” into an in-memory store.
So there you have it – you can either have flexibility, or speed, but not both. But should users accept this restriction?
I first got into the BI game back in the late 90′s, and back then there were systems you could deploy to users, that were both infinitely flexible, and fast; for example, the old Oracle Express Server and its “blue-screen” interface returned data in seconds albeit with fairly primitive client-server, or even DOS-based user interfaces as shown in the screenshot screenshot below (courtesy of the Independent Oracle OLAP Blog – brings back a few memories).
Even now if you go to certain client sites where they’re major users of Excel, you’ll see this sort of response time when they have Analysis Services providing the data, or more recently PowerPivot, Microsoft’s new in-memory, column-store database.
So is it unreasonable for users to ask for both speed and flexibility, especially when they’ve spent millions on license fees for OBIEE, and they’ve got an Exadata server running in the background? I know Express Server and other OLAP tools have their own restrictions, but for sales analysis and other desktop BI applications, from the users’ perspective have we really come all that far in the last ten to twenty years, or is it all excuses now?
Kevin makes the point in his post that perhaps Endeca Information Discovery fills this need now, with its “schema-less” data model and in-memory analysis, and we’ve certainly seen results that would support that – particularly when running Endeca on our Exalytics server, where the Endeca Server engine can leverage the entire 40 cores to massively-parellel query the in-memory data store. But Endeca though comes with its own limitations – there’s no metadata layer, for example, and no obvious support for hierarchies or other “drill to detail” structures, though it’ll be interesting to see how this pans out as Endeca gets integrated into the wider Oracle BI stack, perhaps working together with OBIEE’s BI Server and using the same visualisation layer as the Presentation Server. Essbase of course could also meet this requirement too, but I’m not sure its integration with the OBIEE is quite at the point yet where end-users don’t need to be aware that there’s two different analysis engines running in the background.
So, do you think that it’s fair to say “you can have report flexibility or performance, but not both”, or is that just a limitation in our thinking, or the OBIEE toolset? Do you think having Endeca, or Essbase, in the background now makes this combination possible, or do you feel that, with the right amount of tuning, optimising and preparation, a decently set-up Exadata + Exalytics combination should be able to return results for users within a split-second, regardless of what they throw at it? I’d be interested in readers’ opinions.
Live Virtual OBIEE 11.1.1.7 Expert Seminar with Mark Rittman – April 22nd/23rd 2013, via Oracle University
Can’t make it to one of our scheduled classroom-based OBIEE11g or ODI11g courses, but you’re still keen on hearing the latest about OBIEE 11.1.1.7, Exalytics and Endeca development, and just how far Oracle now are with OBIEE and Essbase/Hyperion integration? If so, Oracle University are running one of my Live Virtual Class “Oracle Expert Seminars” on April 22nd and 23rd 2013, made up of two half-days (afternoons) starting from 12pm GMT and running for around four hours each day.
Here’s the agenda for the two days – assuming OBIEE 11.1.1.7 is out, the material will cover this new release too.
- Oracle BI EE 11g Overview, Architecture and New Features
- Introduction to Oracle Exalytics In-Memory Machine & Oracle TimesTen for Exalytics
- What’s New with Oracle BI EE & Essbase/EPM Suite – Integration and Reporting
- Creating Search/Analytic BI Dashboards using Oracle Endeca Information Discovery
- Integrating Oracle BI EE with Oracle ADF, Oracle WebCenter and Oracle Fusion Middleware
Registration is through Oracle University, however you’ll need to make sure you register soon if you’re interested. Full details are on the event website page, and hopefully I’ll (virtually) see some of our blog readers there!
Rittman Mead BI Forum 2013 Call for Papers now Open!
I’m pleased to announce that the call for papers for the 5th annual Rittman Mead BI Forum is now open, with abstracts being accepted through to January 31st, 2013.
Last year’s BI Forum was the biggest and best ever, running in Brighton, UK and Atlanta, GA in May 2012. This year we’re back again at the Hotel Seattle, Brighton, and moving venues in Atlanta to the Georgia Tech Hotel and Conference Center. As in previous years, the BI Forum is centred around OBIEE and related products such as Oracle Data Integrator, Oracle Endeca, Oracle Essbase and Oracle Database, as well as technologies and concepts such as big data, BI methodology, and BI “best practices”. What makes this event unique is the audience and its size – we keep the numbers to around sixty attendees at each event, the audience is at intermediate-to-expert level, there’s no marketing or sales presentations, the atmosphere is informal, and we concentrate as much on networking and discussions as we do on the actual sessions.
We’ve had some fantastic speakers over the years, presenting on all aspects of OBIEE development, product internals, case studies and project approaches, and we’re proud to have a speaker mix that includes industry experts, Oracle product managers, and presenters that were previously unknown but have gone on to take “best speaker” award. For each of the two events we’ll generally select eight one-hour presentations, and three TED-style ten-minute sessions, and nearer the event we’ll invite suggestions on what this year’s debate will be.
For now though, the call for papers is now open, and you can propose presentations for either the Brighton event, the Atlanta event, or both. At the end of January we’ll invite anyone thinking of attending to vote for their favourite presentations, and we’ll take those votes, along with a bit of “curating” from myself, and publish the agenda.
The call for papers website is here : Rittman Mead BI Forum 2013 Call for Papers – and abstracts will be accepted through to the end of January 2013.
For a roundup of last year’s BI Forum events, including details of the sessions and presentation downloads, you can visit the BI Forum 2012 roundup page on our blog. Any questions, just drop me an email at mark.rittman@rittmanmead.com.