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Informix Error -1251: Unable to create shared memory. semget failed.

Cause and resolution

Unable to create shared memory. semget failed.

Your application is initializing its communication with the database server, which is a version that uses shared memory for communications. An unexpected error has occurred with an operating-system function, semget. Look for operating-system messages that might give more information. Consult with the person who installed the IBM Informix shared-memory product.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-1251 fires when the application, initializing shared-memory communication with the database server, hits an unexpected OS error from semget — per the official guidance, this is an OS-level resource/configuration problem with System V semaphores.

  1. The System V semaphore limit reached on the host, per the official guidance's framing — semget itself failed at the OS level.
  2. A permissions problem preventing semaphore creation for the account involved.
Solutions / Resolution
  1. Consult operating-system messages for additional details, per the official guidance.
  2. Contact the person responsible for installing the IBM Informix shared-memory product, per the official guidance — semaphore/shared-memory kernel parameters are typically tuned as part of that installation.
Examples
Checking System V semaphore limits
$ ipcs -s
$ cat /proc/sys/kernel/sem
Diagnostic Checks
  1. Check OS-level semaphore limits and current usage against what the database server needs.
  2. Check the operating-system error log for the specific semget failure reason.
Related Errors / Related Topics
  • -1250 — "Unable to create pipes." A related connection-initialization error, about pipes rather than shared memory.
  • -1252 — "Unable to create shared memory. shmget failed." A closely related error, about a different shared-memory system call (shmget) failing.

An OS-level semget failure during shared-memory initialization — check semaphore limits and involve whoever installed the shared-memory product.