Recently I have been working on high traffic and highly available web service which is hosted by Siebel. I was asked to improve performance of it. I checked all the places for any performance degradation clues, there was hardly any, all queries were on indexed columns and thin BC's were used, there was no fat whatsoever.
With all the logs and spool generation my focus went to these two problems.
1. Before every web service call Siebel was requesting file system to write read user preference file which was taking fair bit of time due to contention at file system. You might see following in logs, if user preference file is corrupted.
ObjMgrLog Debug 5 0 2016-06-29 06:50:56 SharedFileReader: \SiebelFS\userpref\EAIUSER&Siebel Sales Enterprise.spf: Open iteration 0 failed. errcode = 2.
This file read was absolutely unnecessary, luckily there was a way to turn off by setting "OM - Save Preferences" to FALSE for EAI object manager. This will make all logins to avoid looking up for user preference file.
2. Another useless transaction I noticed was with database. It was when Siebel tries to update the last login date on S_USER record.
In logs you can see queries like these:
UPDATE SIEBEL.S_USER SET
LAST_LOGIN_TS = :7,
MODIFICATION_NUM = :8,
LAST_UPD_BY = :9,
LAST_UPD = :10,
DB_LAST_UPD = current_date,
DB_LAST_UPD_SRC = :11
ROW_ID = :12 AND MODIFICATION_NUM = :14;
This can also be turned off in recent Siebel versions by setting DisableLastLoginTS = TRUE
Its a new parameter introduced by Oracle, you can read more about this parameter on oracle support 1665762.1
Hope it helps. If you have come across any such parameter which can improve performance then please share it in comments below.