Kernel-Managed Swap Facility (KMSF) Manual

Managing KMS Files

Kernel-Managed Swap Facility (KMSF) Manual—425824-005

3-15

Changing the Threshold for Messages

The KMSF generates Event Management Service (EMS) messages when a swap file

passes a preconfigured percent in-use threshold. The default threshold is 85 percent,

that is, when 85 percent of the file is reserved, NSK message 200 is generated.

For default swap files, the threshold is based on the maximum default file size instead

of on the allocated file size. For example, the threshold for default swap files for

systems running G06.27 or later G-series RVUs is 85% of 256 megabytes, or 217.6

megabytes, even if fewer than 256 megabytes are currently allocated for the default

swap file. In Example 3-14 on page 3-15, the threshold for a swap file is given as

13926 pages, but the total number of pages is only 8192.

You can calculate the threshold shown in Example 3-14 as follows:

1 megabyte = 64 memory pages

256 megabytes = 16384 memory pages

85% (16384) = 13926 pages

To alter the threshold for a swap file, use the NSKCOM ALTER command (see page

4-5). In Example 3-15, the threshold is altered to 75 percent.

For complete information on syntax for the ALTER command, see Section 4, NSKCOM

Command Reference.

Example 3-14. Threshold and File Size for Default Swap File

NSK-STATUS SWAPFILE $SYSTEM.ZSYSSWAP.SWAP00

Status of $SYSTEM.ZSYSSWAP.SWAP00

CPU 0

CPU Pages: Total 8192* Reserved 5120 Available 11264

Peak CPU Pages ever reserved 5888

Threshold 13926 CPU pages

* Default swapfile extents may not be fully allocated.

NSK-

Example 3-15. Changing the Threshold for a Swap File

NSK-ALTER SWAPFILE $SWAP.KERSWAP.CPU02A, THRESHOLD 75

File $SWAP.KERSWAP.CPU02A Threshold altered in ZSYSCFG

ALTER was successful: $SWAP.KERSWAP.CPU02A

NSK-