Informix Error -774

Reasons / Common Causes

-774 is the mirror image of -773: it fires when ALTER FRAGMENT supplies a fragment expression against a table using round-robin fragmentation — per the official guidance, round-robin fragmentation distributes rows without any expression-based rule, so a fragment expression isn't meaningful there.

1. ALTER FRAGMENT supplying an expression against a round-robin-fragmented table, per the official guidance — the direct, only cause.
2. A statement written for (or copy-pasted from) an expression-based fragmentation strategy, applied to a table that's actually round-robin fragmented.

Solutions / Resolution

1. Remove the fragment expression, per the official guidance, since round-robin fragmentation doesn't use one.
2. Confirm the table's actual fragmentation strategy before writing the ALTER FRAGMENT statement, the same check as for -773:

   SELECT partn, evaltext FROM sysfragments WHERE tabid =
     (SELECT tabid FROM systables WHERE tabname = 'orders') AND fragtype = 'T';
   -- review the fragmentation strategy for the table
   

3. If expression-based fragmentation was actually intended, that's a bigger change than adding a fragment — round-robin and expression-based are distinct strategies, and switching between them typically requires redefining the table's fragmentation from scratch rather than a simple ALTER FRAGMENT ADD.

Examples

The disallowed attempt

-- orders uses round-robin fragmentation
ALTER FRAGMENT ON TABLE orders ADD FRAGMENT new_dbspace (region = 'west');
-- -774: round-robin fragmentation doesn't take an expression

Corrected — no expression for round-robin

ALTER FRAGMENT ON TABLE orders ADD FRAGMENT new_dbspace;

Diagnostic Checks

1. Confirm the table's fragmentation strategy is round-robin, and remove any fragment expression from the ALTER FRAGMENT statement.

Related Errors / Related Topics

• -772 — "Record/key doesn't qualify for any table/index fragment." A related fragmentation error, specific to expression-based strategies missing a REMAINDER.
• -773 — "Expression required for new fragment." The mirror-image restriction: an expression-based strategy missing its required expression.

The mirror image of -773 — confirm the table's fragmentation strategy first; round-robin never takes a fragment expression.