Informix Error -1791: The database server encountered a fatal error while initializing shared memory.

Reasons / Common Causes

-1791 fires (Windows-specific) when the database server hits a fatal error initializing shared memory — per the official guidance, the specific root cause is recorded in online.log, not in the -1791 message itself.

1. A shared-memory initialization failure, per the official guidance's framing — no specific cause is named beyond directing to online.log for the actual detail.

Solutions / Resolution

1. Examine %INFORMIXDIR%\online.log, per the official guidance, to identify the root cause of this initialization failure.

Examples

Checking online.log

type %INFORMIXDIR%\online.log

Diagnostic Checks

1. Read %INFORMIXDIR%\online.log for the specific shared-memory initialization error recorded there.

Related Errors / Related Topics

• -1251 — "Unable to create shared memory. semget failed." A related, UNIX-side shared- memory-creation error.
• -1252 — "Unable to create shared memory. shmget failed." Another related, UNIX-side shared-memory-creation error.
• -1258 — "Cannot attach to shared memory used to communicate with back end." A related shared-memory error, about the attach step from a client connection rather than server initialization.

A fatal shared-memory initialization failure — check %INFORMIXDIR%\online.log for the specific cause.