struts strts*.tmp files

[Craig Reissener]

What are strts*.tmp files?
We are using struts with our J2EE application running in WebLogic Server 6.1 SP4.
There are a bunch of files named like strts12345.tmp inside the directory config/<MyDomain>/applications/DefaultWebApp/WEB-INF/_tmp_war_*/
They are not human-readable files.
There are about 450MB of them. The files range from 0 bytes to about 27 MB. Some are from today, some are weeks old.
What causes these files to appear? For what are they useful? How could I configure WebLogic to delete them automatically (rather than writing a cron job or some external process that would periodically remove them).
Thanks,
--Craig