The command specified by the PRESNAPSHOTCMD option must complete successfully in order to execute the snapshot differential backup. If the command completed with a return code of 0 (zero), it is considered to have completed successfully. If the command completed with any other return code, it is considered to have failed. If the command failed then the snapshot differential backup is not executed.
The client does not execute the snapshot differential backup operation.
Identify and repair the problem that caused the command to fail. If a non-zero return code is normal for this command, then consider wrapping the command in a script that always exits with a return code of zero.