What have you tried so far?
When did this start? Is this a new deployment?
VM or appliance? is the MNT dedicated or part of a PAN node?
Generally, I'd look at the following, in order of precedence
- Look for Queue Link errors and fix those ASAP
- Check CPU and I/O status (either in your hypervisor or on the SNS server's CIMC)
- If the load on the node is very high then apply Collection Filters to lessen the logging
- Reboot the Primary MNT node to see if that improves it
- Apply latest ISE 3.1 patch to deployment
- Call TAC