important logs are getting purged because of RTR logs. Each time a probe is deleted.
Sep 11 14:57:18.220: a delete request for probe id 29024 found
Sep 11 14:57:29.884: a delete request for probe id 654 found.
Please tell me how can i block such logs
These messages were added in 12.4(3)T and 12.4(3a) as part of a way of indicating that a collector should not be updated if it is about to be deleted. Prior to this, the router would simply crash in that situation.
If you want to stop these messages from coming, add simply reduce the logging severity from debug to informational.