READING/WRITING A DASD PAGE TO/FROK VIRTUAL STORAGE DrtKRPAGT via SYC call to read DASD page into storage. DKKPGTPR ---aelease DASD space that was previously occupied by this virtual
storage page. Remove resident page frames from the user list. DKKPTRFT ---Place these page frames on the free list. Update the SWPTABLE with disk address in RO. DKKPTRAN - Bring the page into storage. QKKRPA, Put real storage address of the virtual page is passed back to the
caller in R2. DKKRP1T ----Entered via SYC call to write out a page to DASD storage. DKKPTR1N Locate the page to be moved and lock it. DKKRPAPT -----store all r.egisters in CPEXBLOK and flag CPEXRO as a write request. DKKPAGIO ---Write the page. Decrement page wait count. If zero results, take user out of page
wait. DKKPTRUL ---unlock the page frame. Return to caller. D!KYATAB -- Entry via BALR when an EC mode virtual machine needs a shadow table
generation and update or purge operation. Get storage to create shadow table, Flag VKBLOK to show shadow table
existance. D!KY1TBC -- Free-shadow page, segment and copy segment, when user leaves EC mode or alters CR o. DKKYATRN to perform third level to first level translations and third
level translations to second level address translations. Use TRANS macro to access virtual segment and page tables to get the virtual
page into real storage. D!KY1TLl - Using the TRANS macro to access the virtual segment and page tables,
pass the resulting page and displacement to DKKPRVLG. DKKY1TPX ----Invoked by D!KPRGIN when a paging exception is received for an EC mode virtual machine. Perform set up operation and develop page table address. Get the page. 1-204 IBM Y8/370 System Logic and Problem Deteraination--Volume 1

DKKVATPX ---Update the shadow table. DKKVATSX -- Invoked by DKKPRGIN when a segment exception is received for an EC
mode virtual machine. DM!{VAT, Perform setup operation, then invalidate the shadow page table or if
none exists, allocate a new shadow table and set it invalid. DMKVATPF via DMKVATPG from DKKPRG to simulate pseudo page fault
interrupts when a paging exception occurs with pseudo page fault
interrupts enabled. DKKPTRAN ' -- BrIng in the DASD page. DKKPRGSK ---aeflect program check X'14' to the user. DMKVAT, PAGRES ---When the--page becomes resident in storage. Build the PGBLOK, set high order bit in the translation exception address field, !!1!KDSP£1! Exit to dispatcher. ALLOCATION AND DEALLOCATION OF DASD SPACE Entry to search and allocate a DASD page for paging/spooling. DMKPGTSG ---Search appropriate RECBLOK chain for available D1SD page. If none
found, locate next available cylinder and construct a new RECBLOK, calculate address of the allocated DASD page and place it in Rl. Return to caller • Entry to deallocate DASD page used for paging and spooling. Via RDEVBLOK locate the RECBLOK and reset appropriate bit in the RECBLOKs RECMAP and adjust the member of DASD pages in use. If all the pages
on the DASD cylinder have been deallocated, deallocate the cylinder.
Exit to caller. Entry to release a group of DASD pages no longer needed for spool
file use. Per Rl, find RECBLOK and dumay RECBLOKs and reset the RECKAP bits as specified. Free related RECBLOKS, if co.plete
deallocation occurs. DKKPGTCG -- Entry for allocation of enough DASD spool space to record a 3704/3705 du.p. Scan RDEVBLOK and associated ALOCBLOK for enough contiguous
available space to record the du.p. When found, flag cylinder as
allocated and build and chain the required RECBLOKs. Dl!KPGTVG ---niiPGT contains an internal table, PAGETABL, in which the allocation
of page frames for the CP paging VKBLOK is kept. The PIGETABL is
scanned for a zero bit denoting the page fra.e is available. The
page is marked allocated by setting the bit to one and the address of
the page fra.e is returned to the caller in Rl. If no page fra.es
are available, a CPEXBLOK is built and queued to the deferred request
chain. DKKPGTVG to release a page of virtual storage. Check the chain of
deferred requests. If there are none, reset the page bit in the PAGETBL to 0 and exit to the caller. Otherwise, give the page to the
first requestor in the deferred chain and stack his CPEXBLOK for the
dispatcher. CP Method of Operation and progra. Organization 1-205