The TechNote that Andy mentioned is the best that I've seen for troubleshooting SQL backup errors. Status 2 is the generic code for SQL agent backup failures.
This is how the TechNote starts:
Analyzing over 500 SQL cases, almost 80% of the cases are opened because of a Status Code 2 being returned by a failed backup:
38 % due to Network Name Resolution.
25% due to a corrupted batch file is, or some 25% are due to missing or incorrect mandatory parameters.
15% due to Backup Policy configuration.
Following, are troubleshooting steps divided into these areas for a SQL backup that fails with Status Code 2.
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MOST important log file is <install_path>\NetBackup\logs\dbclient\<date>.log.
Create the folder if it does not exist and retry the backup. Post dbclient log, please.