Logs produced during synthetic backups
When a synthetic backup is scheduled, NetBackup starts the bpsynth program to manage the synthetic backup process. bpsynth plans how the synthetic backup is built from the previous backup images.
If it is needed, bpsynth schedules the tape drive resources that are needed for the synthetic backup. If the required resources are not available, the job fails with a status code that indicates that a resource is needed.
If the resources can be obtained eventually but not immediately, the synthetic job waits until the resources become available. A synthetic job may wait while a backup, restore, or another synthetic backup job uses a drive.
bpsynth passes the information to programs bptm and bpdm so that tape and disk images can be read or written. Catalog information is managed using bpdbm. Each of these programs has a debug log file in the logs directory.
If problems occur with synthetic backups, the following debug logs are required to diagnose the problem:
On the primary server: bpsynth, bpdbm, and vnetd.
On the media server(s): bpcd, bptm (if any images are written to or from a tape device), and bpdm (if any images are written to or from disk).
Note that several media servers can be involved if the component images are on different nodes.
The log files for synthetic backups are described in the NetBackup Logging Reference Guide.
However, bpsynth is used for each stream or client. To use bpsynth can be inefficient with tape images since bpsynth needs a tape drive to write the new image. Also, bpsynth may use the same component image volumes. One may need to finish before the next can proceed.