RELEASE VIRTUAL STORAGE PAGES DMKPGSSS to release partial virtual storage. Per R1 (address of first
page to be released) and R2 (address of last page to be released) set
partial entry flag. DMKPGSPO -- Entry to check for shared segments and decrement usage count. Store registers and flag full entry condition. Examine V!SHRSYS for shared
segments. If so, decrement use count. On zero use count unchain the SHRTABLE fro. the active list. On NOCEAR exit to caller. If not, store number of release pages in RS. PGOUT£ Locate page and swap tables for the segment to be released and index to the entry for the first page.
DMKPTRAN
Initiate paging, and when paging stops release the page frame. DMKPGS, NEXTPAGE ----S-value-.----- Exit to caller. Entry to release storage containing a named system passed by the
caller. If register one is nonzero, search the page tables looking
for a header equal to the named syste.. If found, release the swap
and page tables and build new ones, if the address range still lies
within the user's virtual storage size. If register one is zero,
release and rebuild swap and segment tables for all segaents above
the normal virtual storage size that do not have SHRT1BLE entries.
FREE STORAGE MANAGEMENT Entry to obtain a block of storage, validate input doublevord request Inn, \nvI· DMK FRE, FREESUB -- ON-subpeeI-size request, index into SUBTABLE. For correct size block
found, remove block from chain and put the address of the block in
R1. Return to caller.
DMKFRE, FREE02 ---Per subpeeI size not found get next large subpool size. Reaove block
from chain, put address in R1 and return to caller.
DMKFRE TRY SPLIT ---Per subpooI-that cannot honor request, start search a 30 doublevord
end for block requirement. When a block is found, split block (if
necessary) and give caller address of his portion in R1 and chain the
remainder to the appropriate subpool size. Return to caller.
DMKFRE, CLEARS1V be found to honor user request, call - Fetch a
storage FREESUB. page from the dynamic paging area. Chain
chain. processing then continues. See it to
entry
CP Method of operation and Program Organization
the free D!KFRE, 1-207

DMKFRERS to return all subpool blocks to the free storage chain per the SUBTABLE reference, as each subpool block is released, its address
and length are placed in R1 and R2 respectively. Branch and link to FRET05 to return the block to the free storage chain (DMKFRELS). Repeat action through all subpools. Return to caller. DMKFRET ----Entry to restore block to subpool or free storage. Per RO and R1
(number of doublewords to be released and and address of the first
double word, respectively), the subpool sized block is returned to
the appropriate subpool. Update the pointer in the SUBTABLE. !!!!I11 If subpool size block being returned is within the dynamic paging area, process as a block of aore than 30 doublewords. Blocks larger than 30 doublewords to be returned are merged into the
free storage chain indicated by DMKFRELs. DMKPTRFT ---Restore page to dynamic page area; if a complete page is alloted,
blocks belonging to the dynamic paging area can be built. Return a block of storage to free storage chain by merging into the
chain storage addresses in an ascending order of sequence. Return to
caller. CP INITIALIZATION AND TERMINATION PROCEDURES D!KCKPT entry point to load the system after loading the first
module, DMKCKP, from the system residence volume. Check CPID in PSA for startup method. For CPID equal to not warm or not CPCP, insert COLD and load the
nucleus. Then branch to DMKCPINT, to perform CP initialization. ON CPID equal to WARM or CPCP, halt and drain all I/O devices and remember enabled terminals. DMKCKP, NEITCH ---nMKRSPCV-to validate warm start cylinder. CLO .£KQ! Save accounting data, log message, SDFBLOKs, and enabled terminals
and lines on checkpoint cylinders. CHKQ2 Save spool records allocation and spool hold queue blocks on
checkpoint cylinder. SHUI2!2 If normal shutdown indicated, issue message to systea operator and
load disabled wait state code 1'008'. 1-208 IBM VM/370 System Logic and Problem Determination--Volume 1