Please have a look at this section of the Upgrade Portal:
The NetBackup 8.1.2 Upgrade Guide provides an upgrade path from NetBackup version 7.7.x through NetBackup 8.1.2. Information about required upgrade steps for older versions of NetBackup are removed from the NetBackup 8.1 and later guides. This change simplifies the upgrade procedure for customers with more current versions of NetBackup.
For a successful upgrade from older NetBackup versions directly to 8.1.2, you must:
Do further assist, do provide more information like:
1) What are the Master/Media servers we are looking at? Traditional or NetBackup Appliances?
2) If traditional, please do look a the following link: https://www.veritas.com/content/support/en_US/doc/NB_80_OSSCL
- If your Master/Media is at RHEL/CentOS/Oracle Linux 6.7 and below you may need to upgrade OS.
3) if is NetBackup Appliances, which model is it?
a) If is 5220, please read this two links:
- NetBackup Appliance 5220 EOSL: https://www.veritas.com/support/en_US/article.100038921
- NetBackup Appliance 5220 MSDP performance degradation for 3.1 : https://www.veritas.com/support/en_US/doc/77080687-125469996-0/v125470004-125469996
This means that 1) 5220 is not supported at 3.1.2, 2) You will not have any form of support for this if there is issues.
b) If is 5230, do log a technical case with support for health check. The support will provide guidance.