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Saturday, April 14, 2018

Application Engine in Process Scheduler: PSAESRV Server Process -v- Standalone PSAE executable

Whether to use the Application Engine server process (PSAESRV) in the process scheduler tuxedo domain or the standalone PSAE executable is a frequently discussed point amongst PeopleSoft administrator.  Over the years, I have written various things on the subject.  I am going to draw them together in this blog, and restate Oracle’s now clear advice about when to use which option.

In PeopleTools 8.4, the Process Scheduler became a fully fledged Tuxedo domain.  The PSAESRV process was also introduced at this time.  It is a persistent process that handles both Application Engine and Optimization Engine requests.  Each server process creates persistent database connections.  A number of these server processes are started with the domain.   The PSAESRV process does not spawn like other Tuxedo server processes.  Instead, you must configure the number of server processes to match the maximum number of concurrent Application Engine process requests and concurrent Optimization Engine requests that the process scheduler can run.  The server was introduced to handle very short-lived Application Engine programs thus avoiding the overhead of instantiating a new process and new database sessions for each process request.  CRM typically uses Application Engine in this fashion, but generally, you do not see this in other PeopleSoft products.

Oracle has not always been clear what they mean by a short-lived process.  It has been suggested that if Application Engine processes are typically taking less than 10-30 seconds, or if you run more than 1000 Application Engine processes requests per hour (note 651970.1) you should use PSAESRVs.
PeopleBooks advises you should use PSAESRV because it delivers improved system performance.  However, PeopleTools Performance Guidelines Red Paper (Doc ID 747389.1) contradicts this somewhat.  Ultimately, if you have any doubts, you should it test each way and determine whether one way gives a clear advantage over the other.

Oracle Support Note "What will be the impact of disabling PSAESRV on the Process Scheduler (Doc ID 651970.1)" explains that if PSAESRV is disabled in the Tuxedo domain configuration, the Process Scheduler goes back to the legacy behaviour and spawns a stand-alone PSAE process for each Application Engine request.  “The Application Engine will take a bit longer to start, [the] time delay may be range from millisecond to seconds” depending on hardware and configuration.

The stand-alone process has several advantages.
  • At the end of the Application Engine program, it disconnects from the database and terminates.  Thus releasing resources from the process and the database session.  Whereas the persistent Application Engine process has been reported to accumulate allocated memory over time.
  • If you are using Oracle database Global Temporary Tables in an application engine, then you should not use PSAESRV because the tables are always created PRESERVE ON COMMIT and so are only released when the database session terminates.
  • If you set any session parameters within an Application Engine program run via PSAESRV, or enable database trace, then these settings will carry forward from one Application Program to the next unless you reset the parameter at the end of the program, or the start of the next.  This is not a concern with standalone PSAE processes.
However, there is at least one case where you must use the server process:
  • If you are using Oracle Active Data Guard and wish to mark some Application Engine programs as read-only then they must be run via the PSAESRV process

Conclusion

  • PeopleTools Performance Guidelines Red Paper (Doc ID 747389.1 sums it up very nicely: “PSAE is as good as PSAESRV for most practical purposes.  If you have an application engine job that runs longer than 10 seconds, PSAE is equivalent to PSAESRV.  PSAE has the added advantage of being recycled at the end of each application engine job, cleaning up any outstanding SQL cursors to the database that may have been left behind.  Because PSAE recycles after each use, PSAE does not have any possible memory leakage problem that may occupy the precious system memory.  In short, PSAE is a cleaner workhorse.”
  • I think it is reasonable to use PSAESRV in CRM.  For all other products, I recommend that PSAESRV should be disabled from all Process Schedulers.
    • If you do have some Application Processes that are both short-lived (i.e. less than 10 seconds) and run frequently, then consider creating other process schedulers with PSAESRV processes that are dedicated to running only these process.  You can then move these processes to a new Process Scheduler category that only runs on these new Process Scheduler.
  • PSAESRV is configured by default, so if you don’t want to use it, and mostly you won’t, then you have to remember to disable it.