A DBXML exception happens under stress test

[hubu]

After create about 150 sessions, MgServer can’t create session anymore. And we will get many errors like below:

Error: An exception occurred in DB XML component.
Error: DB_RUNRECOVERY: Fatal error, run database recovery
StackTrace:
  - MgSiteServiceHandler.ProcessOperation() line 83 file SiteServiceHandler.cpp
  - MgOpCreateSession.Execute() line 109 file OpCreateSession.cpp
  - MgServerSiteService.CreateSession() line 762 file ServerSiteService.cpp
  - MgServerResourceService.CreateRepository() line 541 file ServerResourceService.cpp
  - MgSessionRepository.MgSessionRepository() line 76 file SessionRepository.cpp

This is a regression since we implemented "File-per-Session". After create 150 sessions, the DBxml is locked(hang up), because it can’t allocate memory anymore.

We need to tune DBXML configuration, reduce the log buffer and cache size for session repository.

[hubu]

Fix of this defect

[hubu]

Fixes for trunk submitted in r5779