Informix Error -535: Already in transaction.

Reasons / Common Causes

-535 fires when BEGIN WORK is issued while a transaction is already open on the session — Informix doesn't support nested transactions, so a second BEGIN WORK before the first is closed is redundant and rejected.

1. A program's logic accidentally omits COMMIT WORK/ROLLBACK WORK at the end of a prior transaction, per the official guidance — the next BEGIN WORK then finds one still open.
2. An error-handling path that skips the closing COMMIT/ROLLBACK, so a transaction that should have ended on failure is left open going into the next operation.
3. Nested function/procedure calls each issuing their own BEGIN WORK, without one level being aware the caller already opened a transaction.

Solutions / Resolution

1. Review the program's transaction logic, per the official guidance, to confirm every BEGIN WORK has a matching COMMIT WORK or ROLLBACK WORK on every code path, including error-handling paths.
2. Track transaction state explicitly in application logic if a routine might be called either standalone or nested inside a caller's own transaction, rather than relying on a probe query — Informix has no supported DBINFO/SQLCA field for "is a transaction currently open."
3. Don't nest BEGIN WORK calls — structure the code so only the outermost caller manages the transaction boundary, and inner routines simply participate in the caller's already-open one.

Examples

The redundant BEGIN WORK

BEGIN WORK;
UPDATE orders SET status = 'shipped' WHERE order_id = 42;
-- error-handling path skips ROLLBACK WORK here by mistake
BEGIN WORK;
-- -535: a transaction from the earlier BEGIN WORK is still open

Corrected — close the transaction on every path

BEGIN WORK;
UPDATE orders SET status = 'shipped' WHERE order_id = 42;
-- on error:
ROLLBACK WORK;
-- on success:
COMMIT WORK;

Diagnostic Checks

1. Trace every code path out of the transaction block, especially error/exception handlers, to confirm each one reaches a COMMIT WORK or ROLLBACK WORK.
2. Look for nested routines that each issue their own BEGIN WORK, and consolidate to a single outer transaction boundary.

Related Errors / Related Topics

No closely related error codes are cross-referenced for -535 in this set yet.

Informix transactions don't nest — trace every exit path (including error handlers) from the prior transaction to find the missing COMMIT/ROLLBACK.