Seaquel
SQL Server error code

SQL Server error 2577

SQL Server raises error 2577 at severity 16, which marks a problem with the query or data that you can correct.

Chain sequence numbers are out of order in the Index Allocation Map (IAM) chain for object ID %d, index ID %d, partition ID %I64d, alloc unit ID %I64d (type %.*ls). Page %S_PGID with sequence number %d points to page %S_PGID with sequence number %d.
Msg2577
NameDBCC_IAM_CHAIN_SEQUENCE_OUT_OF_ORDER
Severity16
Group2000–2999

What it means

Every Index Allocation Map (IAM) page has a sequence number. The sequence number is the position of the IAM page within the IAM chain. The rule is that sequence numbers increase by one for each IAM page. IAM page, P_ID2, has a sequence number that does not follow this rule.

Source: Database Engine events and errors