Informix Error -566: Cannot initiate sort.

Reasons / Common Causes

-566 is flagged by the official text as an internal error at the setup stage of a sort — before any rows are actually sorted, distinct from a failure during the sort itself (-564) or reading back already-sorted rows (-565).

1. Insufficient temporary space to even begin the sort, a plausible non-engine-internal contributor even though the official text frames this as internal — the sort couldn't allocate its initial working space in the configured temp dbspace(s).
2. A resource limit reached before the sort could start (available sort-memory buffers, temp-dbspace allocation limits), especially under heavy concurrent load.
3. A genuine internal engine condition, per the official guidance's framing, with no documented application-level cause.

Solutions / Resolution

1. Check the accompanying ISAM error code, per the official guidance, for the specific underlying reason.
2. Check temp-space availability before the sort even runs, since failing at initiation specifically suggests the resource shortage was already present rather than developing mid-sort:

   onstat -d
   

   reviewing free space in the dbspace(s) named by DBSPACETEMP.
3. If this recurs after ruling out a temp-space shortage, note all circumstances and contact IBM Informix Technical Support, per the official guidance.

Examples

Checking temp space before escalating

$ onstat -d
-- review free-page counts for the dbspace(s) listed in DBSPACETEMP
-- before the sort was even attempted

Diagnostic Checks

1. Check the accompanying ISAM error code first, per the official guidance.
2. Check free space in the DBSPACETEMP dbspace(s) as the most plausible concrete contributor, since this fires before the sort can even begin.

Related Errors / Related Topics

• -564 — "Cannot sort rows." Same internal-sort-error family, during the sort itself rather than at initiation.
• -565 — "Cannot read sorted rows." Same family, at the read-back stage.

Part of the same three-error sort-phase family as -564/-565 — check the accompanying ISAM error and temp-space availability before escalating.