Hi Pavan,
If you have requirement to keep the synchronous messages more than 7 days you can change it to longer than 7 days as per this note section 3g872388 - Troubleshooting Archiving and Deletion in PI
g) In case you have configured additional staging and logging steps as described in Note 1760915 message information will also be persisted in BC_MSG_LOG table. The number of entries directly correlates to the number of logging/staging steps you configured and the volume of messages for those interfaces. For asynchronous messages the logged or staged message versions will be deleted automatically when the message from BC_MSG table will be deleted. Synchronous messages are only logged in BC_MSG_LOG without a corresponding entry in BC_MSG table. Therefore these entries have their own retention period specified in parameter "messaging.log.retainTime" under service XPI Service: Messaging System. The value specified here is in days and by default these logged message versions are persisted for 7 days. The logged versions of synchronous messages will also be deleted by the standard PI message deletion job and no additional job has to be scheduled.
There is no restriction for this value, better to keep the value as low as possible, it is completely depends on your requirement, it will occupy more space in the database and it will affect the system performance but if your server have capacity you can increase it.
Regards,
Praveen.