Database backups are a vital part of server management as it is an absolute necessity for data recovery after a catastrophe. The database backup jobs often fail with the SQL error 3266.

As a part of our Server Management Services, we help our customers to monitor and fix similar SQL related errors before it actually affects the backups.

Let us today discuss the possible causes and fixes for this error.

What is SQL error 3266?

Webmasters often notice that the database backups fail with the error 3266 “BACKUP DATABASE is terminating abnormally”. A typical error message looks like:

This error indicates that the filemark in the backup device could not be read.

A filemark for a backup device holds all the details of a backup device like the size of the block, number of blocks in a device, etc.

When a filemark error triggers, SQL Server treats the entire backup media as corrupt and does not write any more data to the backup media.

What causes the filemark error?

The most common reasons that may trigger this error include:

• A media failure on the device that stores the backup.
• A write failure during the creation of the backup.
• Connectivity loss during the network backup procedure.
• Not enough space.
• The database is unable to read the file mark or inaccessibility of the file mark itself.

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How to resolve SQL error 3266?

We can fix this error message with either of the two options given below:

1. Delete the existing backup file
2. Use the format option in the backup script.

As the easy method is to go with the first option, let us discuss that in detail.

With the first option, we must manually delete or erase the device to allow SQL Server to perform new backups to the backup device. We can use the command below for the same:

BACKUP DATABASE mydatabase TO DISK='C:\MyDatabase.bak' with FORMAT

If the error message occurs during a restore operation, it may be possible to retrieve other backup sets from the device by specifying the file number.

To determine if multiple backup sets are on a device, run the following code from Query Analyzer:

RESTORE HEADERONLY FROM DISK='C:\MyDatabase.bak'

Each backup set has one entry in the output. To indicate a specific backup set, use this code:

RESTORE DATABASE mydatabase FROM DISK='C:\MyDatabase.bak WITH FILE = FileNumber

Here, FileNumber is the backup set number we want to restore.

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Conclusion

In short, the database backups often fail with the error 3266 which indicates that the file mark in the backup device could not be read. Today, we saw how our Support Engineers fix this error.