The BUFFERS parameter in the Informix ONCONFIG file specifies the maximum number of shared-memory buffers that the database server user threads have available for disk I/O on behalf of client applications. Therefore, the number of buffers that the database server requires depends on the applications. For example, if the database server accesses 15 percent of the application data 90 percent of the time, you need to allocate enough buffers to hold that 15 percent.

The buffers reside in the resident portion of shared memory and are used to cache database data pages in memory. The more buffers are available the more likely it is that a needed page might already reside in memory as the result of previous request.

If the value for BUFFERS is too high, this means that too much shared memory is allocated without being used.

You can check whether the set size is sufficient for your system in the main screen of the database monitor or with the command onstat –l .

Data Buffers (Informix)

Monitoring Data Buffers (Informix)