Vault duplication jobs compete with other process in NetBackup (such as regularly scheduled backups) for resources, including tape drives. If you want your Vault duplication jobs to obtain resources before other processes, assign a higher priority to the Vault jobs than is assigned to other NetBackup processes.
In addition, using the Any Available storage unit for backup jobs can send some original backup images to the Vault robot. Subsequently, when Vault tries to duplicate those images, it requires a read drive and a write drive in the vault robot. If not enough drives are available, a deadlock condition can occur.
Symantec recommends that you preview the images you want to duplicate before you run the Vault job, which shows you where the images are located and what kind of resources are required to duplicate them.