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Informix Error -637

-637 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.