If necessary, you can perform rolling upgrades in the CASO environment. That is, you can upgrade the central administration server first, and then upgrade the managed media servers over a period of time. Symantec recommends that you do not keep a mix of versions in the CASO installation for an extended time. Key functionality for administering managed media servers is missing in a mixed-version environment, and decreases your ability to properly administer the CASO environment.
After you upgrade the central administration server to Backup Exec 12.5, the following operations are supported on managed media servers that run Backup Exec 12:
If the catalogs were located on the central administration server, they remain there after the upgrade. If the catalogs were located on the managed media servers, then after the upgrade, they are distributed between the managed media servers and the central administration server.