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SQL Server error code

SQL Server error 2527

SQL Server raises error 2527 at severity 16, which marks a problem with the query or data that you can correct.

Unable to process index %.*ls of table %.*ls because filegroup %.*ls is offline.
Msg2527
NameDBCC_INDEX_FILEGROUP_IS_OFFLINE
Severity16
Group2000–2999

What it means

This informational message indicates that the index cannot be checked because one of the filegroups that stores data for the index is offline. The state of the files in a filegroup determines the availability of the whole filegroup. For a filegroup to be available, all files within the filegroup must be online. If there are no other problems, all other indexes of the same object will be checked.

Source: Database Engine events and errors