How can we generate log on client and server level?

Siebel Logs can be used for debugging at the client and server level.

Dedicated client
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Right click on Siebel Client icon or Shortcut
In Target Text Field, append the following string at the end: /u <username> /p <password> /s "c:MySiebelLog.txt"

This will generate all the SQL statements generated against the database.

Web client
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Increase the Trace and SQL Trace level of the server component (object manager or other components) to 8 to dump all the possible info. You need to have access to the file system on Siebel app server to see these logs.