Tuesday, September 29, 2009

How to clear appserver cache without shutting it down


It is often necessary to clear the physical cache files on the PeopleSoft application server. You would think that after all the length of time that PeopleTools has been around, that development would have sorted out the problems in object version numbering. Sometimes, recently migrated changes do not take effect until the cache is cleared. Global Support will nearly always ask you to clear the cache if you are experiencing any kind of problem in the PIA.

Normally, you would shut down the application server, delete the physical cache directories and restart the application server.

From PeopleTools 8.48, each Application server process can only use one dedicated set of physical cache files that is in a directory whose name includes the name and ID number of the server, (previously the server process could use any unlock set cache directories). This allowed PeopleSoft to add an option to the psadmin utility to trigger each PSAPPSRV process to clear out its own physical cache. This option also causes each server process to recycle. It is the recommended and supported way to clear the physical cache files.

This can also be invoked from the command line

psadmin -c purge -d <domain> [-noarch | -arch <archive_directory>] [-log <"log_comments">]
where 'domain' specifies domain name in PS_HOME and
'archive_directory' specifies location to which to quarantine the purged cache,
'log_comments' specifies any comments to be added to the purge cache log entry


However, even in previous versions, there has always been a way to invalidate all physical cache files. Any cached object older than the value of LASTREFRESHDTTM on the table PSSTATUS (it was on a different table prior to PeopleTools 8) is purged from the cache when the process that references that cache starts. Therefore, if that value is updated to the current time, the entire cache will be purged.

UPDATE PSSTATUS
SET LASTREFRESHDTTM = SYSDATE
/
COMMIT
/

Sometimes, developers also have to clear the physical cache on their clients used by Application Designer. Updating PSSTATUS also clears two-tier client caches. In fact, this behaviour is left over from the days when PeopleTools was a two-tier application, and it was necessary to clear cache files on users' desktop computers.

  • If you have multiple Application Servers on a single database, then you can shut each one down in turn without any loss of server. The users will fail over to the surviving servers. However, this can result in the load being unevenly distributed and could overload one server.
  • In small environments, and this includes most development and test systems, there is only a single application server. Shutting down an application server requires downtime and can be disruptive.



Remember, that users will experience a reduction in performance after clearing the cache because it needs to be rebuilt by querying the PeopleTools table.

The Process Scheduler, Master Process Scheduler, Distribution Server, and Application Engine processes also have physical caches. These are also cleared when LASTREFRESHDTTM is updated and the processes restarted. However, you should not shut down the Process Scheduler while processes are executing. The server process will shutdown and the Application Engine will be killed if using an Application Engine server process (PSAESRV). Any stand-alone processes, including psae, will be killed by the Process Scheduler when it is restarted.


 

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