Hi,
Your current SEPM version supports the direct upgrade to the latest version (12.1.4 MP1a). Steps you will need to do:
1. Perform Symantec Disaster Recovery Proceedure
- Backup SEPM database and Server Private Key
2. Disable the replication on both SEPM server (monitor if your clients are reporting on your primary SEPM)
3. You can now directly upgrade your SEPM server on the latest version.
4. Upon successful upgrade of the primary server you also need to upgrade your second server (replication partner). This is to synchronize the SEPM version prior to the replication
5. After upgrading both SEPM servers and all your clients are reporting properly, you can now proceed on your replication.
Hope this summarize steps somehow helps you.
Best Regards,