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What is a shared memory dump?

Technote (FAQ)


This document explains what is a shared memory dump generated by a IBM® Informix® Dynamic Server (IDS) instance.


What is shared memory dump?

An IBM® Informix® Dynamic Server shared memory dump is a file that contains a complete copy of the shared memory used by IDS instance.

What it does

A shared memory dump is usually created when the IDS instance encounters a problem and generates an assertion failure. Since it contains the shared memory information used by the IDS instance at the moment of the assertion failure, it provides valuable diagnostic information for technical support analysts.

What products have it

This feature is available only in these products and versions.

Product Name
Product Version(s)
Hardware Vendor
Operating System
IBM Informix® Dynamic Server
x can be T, U, H, or F depending on your operating system.

How to use it

The shared memory dump generation is controlled by a configuration parameter called DUMPSHMEM. By default it is set to 1, which means that IDS will generate the memory dump in case of an assertion failure.
All the shared memory that the database server uses is dumped so the file is probably quite large. The shared memory dump is placed in the directory that the configuration parameter DUMPDIR specifies.
Send the shared memory dump file along with the assertion failure file when requested by a technical support analyst.


This example shows part of the IBM® Informix® Dynamic Server message log that reports an assertion failure and the shared memory dump file creation.

18:29:21  Assert Failed: found errno 201 in session 16
18:29:21  IBM Informix Dynamic Server Version 9.40.UC5
18:29:21   Who: Session(16, informix@killa, 3536, 11240ef8)
                Thread(67, sqlexec, 112120d8, 1)
                File: rsdebug.c Line: 3721
18:29:21   Action: Use onmode -i to allow Dynamic Server to continue.
18:29:21  stack trace for pid 3469 written to /tmp/af.42bc1c0
18:29:21   See Also: /tmp/af.42bc1c0, shmem.42bc1c0.0
18:29:27  found errno 201 in session 16

In this case the name of the assertion failure file is af.42bc1c0 and the shared memory dump file is shmem.42bc1c0.0.

Document information

More support for: Informix Servers

Software version: 11.1, 11.5, 11.7, 12.1

Operating system(s): AIX, HP-UX, Linux, Solaris, Windows

Reference #: 1207356

Modified date: 29 July 2013

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