Informix Error -621: Unable to update new lock level.

Reasons / Common Causes

-621 is flagged by the official text as an internal error: the server can't convert a lock from shared to exclusive — per the official guidance, possibly reflecting a hardware error or a shared memory problem.

1. A hardware error, per the official guidance — the first specific possibility it names.
2. A shared-memory problem in the instance's memory segments, per the official guidance — the second specific possibility.
3. An underlying ISAM-level error during the lock conversion, per the official guidance's pointer to checking the accompanying ISAM error code.

Solutions / Resolution

1. Check the accompanying ISAM error code, per the official guidance, for the specific underlying reason.
2. Check for hardware errors on the host, per the official guidance — OS-level hardware/disk logs, memory diagnostics.
3. Check the instance's shared-memory health, per the official guidance:

   onstat -
   

   reviewing the summary status for any shared-memory-related warnings.
4. If this recurs, note all circumstances and contact IBM Informix Technical Support, per the official guidance.

Examples

Checking instance and hardware health

$ onstat -
-- review the summary status line for shared-memory-related warnings

$ dmesg | tail -50
-- check for OS-level hardware error messages around the time of the failure

Diagnostic Checks

1. Check the accompanying ISAM error code first, per the official guidance.
2. Check for hardware errors and shared-memory health, per the official guidance's two named possibilities.

Related Errors / Related Topics

• -620 — "Unable to update next extent size." Another internal error in the same general family, pointing at possible root dbspace corruption rather than hardware/shared-memory issues.
• -622 — "Error on locating constraint index index-name." Another internal error in the same family, pointing at possible system-catalog or root dbspace corruption.

An internal lock-conversion failure — check for hardware errors and shared-memory health, per the official guidance's two named possibilities.