Seaquel
SQL Server error code

SQL Server error 2511

SQL Server raises error 2511 at severity 16, which marks a problem with the query or data that you can correct.

Table error: Object ID %d, index ID %d, partition ID %I64d, alloc unit ID %I64d (type %.*ls). Keys out of order on page %S_PGID, slots %d and %d.
Msg2511
NameDBCC_KEYS_OUT_OF_ORDER
Severity16
Group2000–2999

What it means

Out-of-order keys were detected in the specified index. The page in which the keys are contained may be corrupted.

Source: Database Engine events and errors