Parameter Type: Integer
Default Value: 64kB
Range: 32kB to system dependent
Minimum Scope of Effect: Cluster
When Value Changes Take Effect: Restart
Required Authorization to Activate: EPAS service account
The amount of memory used in shared memory for WAL data. The default is 64 kilobytes (
64kB). The setting need only be large enough to hold the amount of WAL data generated by one typical transaction, since the data is written out to disk at every transaction commit.
Increasing this parameter might cause Advanced Server to request more System V shared memory than your operating system's default configuration allows. See the section “Shared Memory and Semaphores” in the PostgreSQL Core Documentation for information on how to adjust those parameters, if necessary.
Although even this very small setting does not always cause a problem, there are situations where it can result in extra
fsync calls, and degrade overall system throughput. Increasing this value to 1MB or so can alleviate this problem. On very busy systems, an even higher value may be needed, up to a maximum of about 16MB. Like
shared_buffers, this parameter increases Advanced Server’s initial shared memory allocation, so if increasing it causes an Advanced Server start failure, you will need to increase the operating system limit.