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Informix Error -637: Cannot alter optical cluster.

Cause and resolution

Cannot alter optical cluster.

An attempt to alter the size of an optical cluster has failed. See the ISAM error for more information.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-637 fires when altering the size of an optical cluster fails for a reason the accompanying ISAM error identifies — per the official guidance, this error itself is a general failure indicator, the alter-side counterpart to -632's creation failure and -633's drop failure.

  1. An underlying ISAM-level error during the alter operation, per the official guidance's pointer to checking the accompanying ISAM error — the only documented path to the specific cause.
  2. Optical Subsystem-level storage issues (the optical media/jukebox/library being unavailable, full, or misconfigured), a plausible category of cause given the subsystem involved, though not explicitly named by the sparse official text.
  3. A requested new size violating one of -636's cluster-key limits (column count or CHARACTER width), if the alter operation involves changing the cluster key itself.
Solutions / Resolution
  1. Check the accompanying ISAM error code, per the official guidance — this is the only documented path to the specific underlying cause.
  2. Check whether the requested change would violate -636's cluster-key limits, if the alter involves the cluster key's composition.
  3. Check Optical Subsystem storage availability (media, jukebox/library status) as a plausible contributor, similar to -632/-633.
Examples
Checking the accompanying ISAM error
-- Review the ISAM error code reported alongside -637 for the specific
-- underlying reason the optical cluster's size couldn't be altered.
Diagnostic Checks
  1. Check the accompanying ISAM error code first, per the official guidance.
  2. Check the requested change against -636's cluster-key limits if applicable.
Related Errors / Related Topics
  • -631 — "Cannot create optical cluster on column that is not TEXT or BYTE." Related optical-cluster restriction on column type.
  • -632 — "Cannot create optical cluster." The creation-side general failure.
  • -633 — "Cannot drop optical cluster." The drop-side general failure.

The alter-side counterpart to -632/-633 — the accompanying ISAM error carries the specific reason, per the official guidance.