SHARED SEGMENT STORAGE MANAGEMENT Entry via SVC from STORE command is to
the CP command will
a private copy. DPIKERMSG the command processor if an ADSTOP, TRACE, or
alter a shared page. The virtual machine issuing
be unshared from the named system, that is, given ---rhe-running virtual machine is informed of the share page violation. Entered from DMPDSP or DMKPTR via BALR. The protected shared page
tables are examined for hardware change bit being on. The resulting
condition code is reflected to the caller. Entered to switch the virtual machine from one set of page tables to
the other. TEPIPORARY DISK STORAGE MANAGEMENT DMKTDKGT to allocate temporary disk space (T-disk). With RO equal to
the number of cylinders required and R1 equal to the device type,
locate RDEVBLOK and related ALOCBLOK's ALOCMIP. If no allocation
space is to be found, return to caller with 0 in RB. If allocation
is successful, flag ILOCMIP, with X'AA' as allocated and put first
cylinder address in R1 and RDEVBLOK pointer in RS and return to
caller. PAGING I/O SCHEDULER DMKPAGIO -- Entry to initiate Page I/O activity. Using preformatted IOBLOK from lOBSTICK, fill in the CCWs with DASD opcode and values derived from CPEXBLOK swap table and core table. Chain the CPEXBLOK on the
in-transit queue. Q!KPA§, Find the Paging RDEVBLOK. FI!Q!Q!! Search IOBLOKs seeking the same cylinder address. If found, chain
the channel programs together with TICs. DMKDSPCH the dispatcher. If no IOBLOKs with some cylinder address are found - Start the I/O operation. DMKDSPCH ----EiIt-to the dispatcher to await interrupt. Upon interrupt return, unchain the CPEXBLOK from the intransit queue. DMKSTPCP ---Stack all deferred requests for execution. Return IOBLOK to lOBSTICK or free it. Calculate paging load and store it, the TOD, and other values in PSI. DMKDSPCH ---ExIt-to dispatcher. 1-206 IBPI VPI/370 System Logic and Problem Determination--Volume 1

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