VSTOR - Virtual Storage Activity report

The Virtual Storage Activity report provides information about the use of virtual storage that can help your installation manage its use of virtual storage.

The report is formatted into the following five sections, each with a separate subheading:

COMMON STORAGE SUMMARY (see Common Storage Summary section )
COMMON STORAGE DETAIL (see Common Storage Detail section )
PRIVATE AREA SUMMARY (see Private Area Summary section )
PRIVATE AREA DETAIL (see Private Area Detail section )
HIGH VIRTUAL MEMORY USAGE (see High Virtual Memory Usage section )

Most of the information you need to begin managing virtual storage appears in the common storage summary report. When this report indicates a problem, you can request one of the three more comprehensive reports for additional information. The structure and fields of the different reports are described in Contents of the report.

Free and allocated storage

All of the four report sections define virtual storage space as either free storage or allocated storage. Free storage is any block of at least 4K (4096 bytes) that contains no storage obtained via the GETMAIN macro instruction. Allocated storage is any block of at least 4K that contains any storage obtained with the GETMAIN macro instruction. Thus, for the purposes of the report, free storage within a 4K block assigned to a subpool is allocated storage. Both free storage and allocated storage are reported as a multiple of 4K on the reports.

Using the information given in the report

Information on virtual storage use is particularly helpful in the process of long-term measurements. It helps you, for example, understand your current use of virtual storage, see the relationship between increased use of your system and increased demands on virtual storage, and predict future constraints before they occur. This ability to predict a future constraint is useful for the virtual storage resource because actions that can relieve a virtual storage constraint generally require significant time to plan and implement. The report can also help you determine the effect of any actions, such as moving a large application above the 16-megabyte line or installing products that take advantage of expanded addressing.

The information in the report can help you identify any expansion of SQA into CSA and set appropriate size values for CSA Start of change , RUCSA, End of change and SQA at IPL time. You can use the report to verify the cost (in increased PLPA inter-module space) of any pack lists your installation uses to reduce PLPA paging.