DMKCKS, If the change is applicable to a SHQBLOK (hold queue block), make appropriate change on the checkpoint cylinder. DMKCKS, CKSPL1 the-change is applicable to a SFBLOK, either add, change, or
delete it on the checkpoint cylinder. DMKCKS, CKSPL5 -- If-the--change affects START or DRAIN command
cylinder.
a spooling device RDEVBLOK (for example, a
issued), mark the change on the checkpoint DMKCKS, CKSEIIT ---unIock:the-routine. Unlock the page map and exit to caller. DMKCKSWM via DMKCPI during VM/370 reinitialization process whenever the
records for closed spool data need to be reconstructed. Get a virtual
page for the map of the checkpoint cylinder and set up the device
code of the system residence volume. In addition, set up local data
areas. For slots having real device entries, set or reset the RDEVDISA and RDEVDRAN and move in the check pointed device classes into RVDEVCLAS. 12MKCKS, For slots containing spool hold queue block, chain this to the SHQ chain. CK S !!1J Get storage for SFBLOK space and set flags depending upon its last
checkpoint activity. DMKCKS, CKSWM4 If the fIle SFBLOK was active, chain it to the appropriate printer,
reader, or punch chain. J2!1KCKS, CKS!M5 Allocate the DASD buffers of the spool file by reading each buffer to
determine the next one and then allocate this DMKCKS, ror the dump spool file, the buffers are allocated sequentially from
the beginning to the end. DMKCKS, CKSWM9 ---Set up the-map delimiter for the end of non-empty slot; then set up a
new spool file identity (spoolid) higher than existing numbers.
Return to DMKWRM. INTER-VIRTUAL MACHINE COMMUNICATION DMKVMCFC from DMKHVC and the DIAGNOSE instruction code X'68'. Builds a YMCBLOK and initializes it with data from the user's parameter list, VMCPARM. The virtual address of VMCPARM is contained in bits 8-11
(rx) of the DIAGNOSE instruction. DMKVMC, Branch table to pass control to the appropriate subroutine based on
the subfunction code in VMCPARM. CP Method of Operation and program Organization 1-225

Subfunction
Code X' 0000' X'OOOl' X'0002' X'0003' X'0004' X'0005' X'0006' X'0001' X'OOOS' X'0009' X'OOOA' VMCAUTH VMCUAUTH VMCSEND VMCSENDR VMCSENDX VMCRECV VMCCNCL VMCREPLY VMCQIES VMCRESUM VMCIDENT Notifies a virtual machine of a pending VMCF communication by posting
a special external interrupt X'4001' unless: • There is already a special external interrupt posted. • The virtual machine is running disabled for VMCF interrupts (PSi bit 1 and CRO bit 31). Transfers data from one virtual storage to another virtual storage.
Errors occurring during data transfer are reflected to originating
virtual machine via the data transfer return code in the final
response interrupt message header. DMKVMCEX ---Called from DMKDSP to reflect an external interrupt message header to
a virtual machine. If the VMCF subfunction is a SENDX, the SOURCE data is moved into the external interrupt buffer immediately
following the message header. DMKVMCUA ---Called by DMKCFP when a virtual machine is logged off or reset. Uses the VMCUAUTH subroutine (subfunction code X'OOOl') to dispose of
existing VMCBLOKS before turning off virtual machine communication.
1-226 IBM VM/310 System Logic and Problem DeterMination--Volume 1