Loading/paging out virtual storage areas

The PGLOAD, PGSER LOAD, and DSPSERV LOAD essentially provide a page-ahead function. By loading specified address space and data space areas into central storage, you can attempt to ensure that certain pages will be in central storage when needed. Page faults can still occur, however, because these pages may be paged out if not referenced soon enough.

Loading and paging for address spaces: With the page load function, you have the option of specifying that the contents of the virtual area is to remain intact or be released. If you specify RELEASE=Y with PGLOAD or PGSER LOAD, the current contents of entire virtual 4K pages to be brought in may be discarded and new real frames assigned without page-in operations; if you specify RELEASE=N, the contents are to remain intact and be used later. If you specify RELEASE=Y, the page release function will be performed before the page load function. That is, no page-in is needed for areas defining entire virtual pages since the contents of those pages are expendable.

Note: PGRLSE, PGSER RELEASE, PGSER FREE with RELEASE=Y, and PGFREE RELEASE=Y may ignore some or all of the pages in the input range and will not notify the caller if this was done.

Any pages in the input range that match any of the following conditions will be skipped, and processing continues with the next page in the range:

Storage is not allocated or all pages in a segment have not yet been referenced.
Page is in PSA, SQA or LSQA.
Page is V=R. Effectively, it's fixed.
Page is in BLDL, (E)PLPA, or (E)MLPA.
Page has a page fix in progress or a nonzero FIX count.
Pages with COMMIT in progress or with DISASSOCIATE in progress.

Loading and paging for data spaces: DSPSERV LOAD requests the starting address of the data space area to be loaded and the number of pages that the system is to load. It does not offer a RELEASE=Y or a RELEASE=N function.

PGOUT, PGSER OUT, and DSPSERV OUT initiate page-out operations for specified virtual areas that are in central storage. For address spaces, the real frames will be made available for reuse upon completion of the page-out operation unless you specify the KEEPREL parameter in the macro. An area that does not encompass one or more complete pages will be copied to auxiliary storage, but the real frames will not be freed. DSPSERV LOAD does not have the KEEPREL function.

The proper use of the page load and page out functions tend to decrease system overhead by helping the system keep pages currently in use, or soon to be in use, in central storage. An example of the misuse of the page load function is to load ten pages and then use only two.

For more information on DSPSERV LOAD and DSPSERV OUT, see Paging data space storage areas into and out of central storage.