DMKGRF, RDATA ---Process-read response of data plus ENTER key. DMKCNSED modify length count. Move data to caller's buffer. Schedule rewrite to screen (unless inhibited) • QMKIOS2R Perform start I/O. DMKDSPCH dispatcher. DMKGRFIC ---intry point to process CONTASKS queue for local 3270 and 3066 devices.
DMKFREE for IOBLOK and TRQBLOK.
DMKGRF, BLDCCWS if appropriate. If not - DMKDSPCH dispatcher. DMKGRF, RDMINT read-return, determine function key action and write response (if
appropriate) via KEITEL.
DMKGRFTI point for processing timer interrupts. LOCATE AND VALID1TE AN 151M READ SEQUENCE Entry from D!KCCW modules to locate and modify an lSI! CCW string. Using the IOBLOKs IOBC1W locate the RCWT1SK. Check for the lSI! read CCW. CHK!Q Check for the correct 151M sequence as follows: 1. The last CCW in the RCWTASK is a TIC. 2. This RCWTASK points to the next RCWT1SK with a minimum of 2 CCWs. 3. The first modified CCW is in real storage.
4. The last byte of the 151M read overlays the operation code of
the first CCW in the next RCWT1SK. 5. The TIC in the RCWT1SK is to the next RCIT1SK's first CCW. 6. The date address of the first CCI in the next RCIT1SK is the same address of the lSI! read+1 as it is in real storage. DMKFREE ---Storage obtained for seven double words save block. DMKISM, CHKTSK2 -- Institute-the 151M read modification as follows:
1. Set the read to point to the save block data area.
2. Set the CP TIC to point to the modified CCI in the same block.
3. Set the modified CCI (seek head) in the save block to point to
the save block data area.
4. Set the CP TIC in the save block to return to the RCIT1SK following the modified (seek head) CCW. 5. Set the search cel in the RCWTASK to point to the data area in
the same block.
1-194 IBM VM/370 System Logic and Problem Deter.ination--Volume 1

DOUBLEWORD SAVE BLOCK Read Address I (2) TIC Address Unused Read Data Area I I (3) !odified CCW (4) TIC to RCWTASK Real Read CCW Real TIC CCW Return to DKKCCW module via SVC 12. SCHEDULING CP lND VIRTUAL I/O OPERATIONS AND INTERRUPTION HANDLING Entry to process CP generated I/O. Flag the IOBLOK as a CP generated
event. Initiate I/O if path to real device is free (available). If
not, queue the IOBLOK and return to caller. Entry to process I/O for virtual aachine I/O operations. !ark IOBLOK as not CP initiated. Save V!BLOK address. If path to the VDEVBLOK or the VDEVBLOK is busy queue the IOBLOK and return to caller. If available status, start the I/O and return to caller. DMKIOS, IOBSTART ---rl-I/o--request has not been reset, save the address of the active IOBLOK and set device busy. If the device is being reset, unflag
scheduled device and scheduled control unit. Stack the IOBLOK and
restart the device. IOS§!Q Set the subchannel path busy and chain the active IOBLOK fro. the RDEVBLOK. DMKIOS, IOSSIO CAW and issue the SIO. Check SIO co.pletion.
Returned condition code sets sequel action.
cc = 0 indicates successful start
cc = 1 CCW stored, initiate sense operation
cc = 2 Busy condition, retry or requeue IOBLOK cc = 3 Fatal error (not operational), stack the IOBLOK and return to
caller
CP Kethod of Operation and prograa Organization 1-195