DUMPSHMEM configuration parameter (UNIX)

Use the DUMPSHMEM configuration parameter to indicate whether a shared memory dump is created on an assertion failure. This configuration parameter also specifies how much memory is written to the shmem.pid.cnt file in the directory specified by the DUMPDIR configuration parameter.

onconfig.std value
DUMPSHMEM 1
values
0 = Do not create a shared memory dump.

1 = Create a shared memory dump of all the shared memory that the database uses.

2 = Create a shared memory dump that excludes the buffer pools.

5 = Enables the managed shared memory dump feature. When permitted, create a shared memory dump of all the shared memory that the database uses.

6 = Enables the managed shared memory dump feature. When permitted, create a shared memory dump that excludes the buffer pools.

takes effect
After you edit your onconfig file and restart the database server.
When you reset the value dynamically in your onconfig file by running the onmode -wf command.
When you reset the value in memory by running the onmode -wm command.

Usage

If DUMPSHMEM is set to 1, all the shared memory that the database server uses is dumped, which can result in a large file. When space is limited, set DUMPSHMEM to 2 because this setting creates a smaller shared-memory dump file.

The values of 5 and 6 enables the managed shared memory dump feature. This determines whether or not a shared memory dump will be created depending on the type of Assertion Failure and how many shared memory dumps may have already been created by the thread or instance. When enabled the feature manages concurrent shared memory dump requests according to the type of Assertion Failure:
  • A non-fatal request (AFWARN, AFFAIL) will be ignored if a shared memory dump is already in progress. The requesting thread will continue immediately.
  • A fatal request (AFCRASH) will block the requesting thread if a shared memory dump is in progress. The thread is allowed to continue upon completion of the shared memory dump.

The DUMPCNT onconfig parameter provides options to control the working of the feature.

The pid value is the process identification number for the virtual processor. The cnt value increments each time that this virtual processor encounters an assertion failure. The cnt value can range from 1 to the value of the DUMPCNT configuration parameter. After the value of DUMPCNT is reached, no more files are created. If the database server continues to detect inconsistencies, errors are reported to the message log (and perhaps to the application), but no further diagnostic information is saved.