Informix Error -21521: More than 1 online index operation on the same table

Reasons / Common Causes

-21521 fires when more than one online index operation is attempted on the same table concurrently — per the official guidance, this isn't allowed.

1. A second online index operation attempted on a table while one is already in progress, per the official guidance — the direct, only cause.

Solutions / Resolution

1. Wait for the in-progress online index operation to complete before starting another on the same table, per the official guidance.

Examples

N/A

No specific triggering statement is documented beyond overlapping online index operations on one table.

Diagnostic Checks

1. Check whether another online index operation is already running against the same table, and wait for it to finish.

Related Errors / Related Topics

• -21511 — "Cannot request more than 1 page for online index build." A related online-index-build internal error, on page-request count rather than concurrent operations.
• -21522 — "No online index build possible." A related online-index-build restriction, on the build being unsupported for the scenario at all.

More than one online index operation was attempted on the same table at once — wait for the first to complete.