IT Management

MVS Boot Camp: Monitoring Virtual Storage Consumption

2 Pages

Are your OS/390 applications experiencing virtual storage constraints? If you don’t know and don’t know how you can find out, then this article is for you. Some applications, such as DB2, use a tremendous amount of “above the line” virtual storage. If the virtual storage consumption is not monitored, you could unexpectedly experience virtual storage constraints, leading to application failures. Monitoring virtual storage consumption is one step you can take toward proactive capacity planning in your environment. This article will demonstrate how you can use IBM’s RMF product to monitor the virtual storage utilization of specific address spaces running on your system.

When an OS/390 address space is created, up to 16MB of memory is allocated below the 16MB line, and up to 2GB of memory is allocated above the 16MB line. RMF provides a function to map this virtual storage. With a bit of calculation, you can quickly see how much free space is available within your address space(s) virtual storage allocation.


In order to monitor an address space’s virtual consumption, the first thing you need to do is direct the RMF product to gather the virtual storage statistics for a given address space. The simplest way to accomplish this is to issue a “modify” command to the RMF application. The following console command will tell RMF to monitor the virtual storage for a DB2 address space named PRDADBM1:


After entering the command, watch the SYSLOG for any error messages. You should see console messages similar to those shown in Figure 1. Once the RMF command has been successful, wait a few moments for the statistics to be gathered. (You should wait until at least two of your RMF intervals [or SMF intervals if you use SYNC(SMF)] have passed before proceeding to the next step.)

NOTE: You can find the SMF interval in the INTVAL(mm) statement in SYS1.PARMLIB(SMFPRMxx), and the RMF in the INTERVAL(mm) statement in SYS1.PARMLIB(ERBRMFxx).


2 Pages