PSYBK

Prolog  

Control Block Contents  
   PSYBK DSECT

Storage Layout  

Cross Reference (Contains links to field and bit definitions)  

PSYBK Prolog

 Name       : HCPPSYBK
 Description: Persistent System Permanent Free Storage
              Frame Header Control Block
 DSECT      : PSYBK
 Function   : Map the header of Persistent System Permanent
              Free Storage frames
 Located by : PRQHDR, PSYFWD
 Created by : HCPFRDPR
 Deleted by : HCPFRET
 Serialized : Regular free storage frame serialization -
              FSDVMLK located at HCPRSMFL
 Notes      : PSYBKs are always, and only, allocated as the very first
              block in PERSYS free storage frames.  They serve as the
              PERSYS free storage frame header, and are pre-allocated
              out of the frame before the first request for which the
              frame was obtained is satisfied and allocated.  All
              PERSYS free storage frames must have a PSYBK as the first
              control block, and no PSYBKs may be allocated anywhere
              else.  PSYBKs are only deleted when the PERSYS free
              storage frame is otherwise empty and the frame is being
              reclaimed and returned to the available list for other
              uses.

PSYBK Control Block Content

PSYBK DSECT

Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      PSYBK          Persistent System Permanent Free
                                        Storage
0000    0 Signed       4 PSYFWD         Forward pointer to the next
                                        persistent free storage frame's
                                        PSYBK header, or PRQHD address if
                                        this is the last PSYBK on the
                                        queue.
0004    4 Signed       4 PSYBWD         Backward pointer to the previous
                                        persistent free storage frame's
                                        PSYBK header, or PRQHD address if
                                        this is the first PSYBK on the
                                        queue.
0008    8 Bitstring    1 PSYCODE        FRMCODE that must match FRMCSB0
                                        and be equal to FRMPERSY for
                                        persistent free storage frames
                                        and their PSYBK headers
0009    9 Bitstring    3 *              Reserved for IBM use
000C   12 Signed       2 PSYVMFRG       Shadow copy of FRMVMFRG so that
                                        we can restore persistent free
                                        storage FRMTE after a bounce
000E   14 Signed       2 PSYDWUSE       Shadow copy of FRMDWUSE so that
                                        we can restore persistent free
                                        storage FRMTE after a bounce
0010   16 Signed       4 PSYCHN         Shadow copy of FRMCHN so that we
                                        can restore persistent free
                                        storage FRMTE after a bounce
0014   20 Signed       4 *              Reserved for IBM use
0018   24 Dbl-Word     8 PSYTODST       "Base" IPL TOD timestamp. This is
                                        the TOD timestamp of the original
                                        IPL since which PERSYS storage
                                        has survived.
          00000020       PSYLEN         *-PSYBK Length, in bytes, of
                                        PSYBK
          00000004       PSYSIZE        (*-PSYBK+7)/8 Size, in
                                        doublewords, of PSYBK

PSYBK Storage Layout

          
*** PSYBK - Persistent System Permanent Free Storage
*
*     +---------------------------+---------------------------+
*   0 |          PSYFWD           |          PSYBWD           |
*     +------+--------------------+-------------+-------------+
*   8 |:CODE |////////////////////|  PSYVMFRG   |  PSYDWUSE   |
*     +------+--------------------+-------------+-------------+
*  10 |          PSYCHN           |///////////////////////////|
*     +---------------------------+---------------------------+
*  18 |                       PSYTODST                        |
*     +-------------------------------------------------------+
*  20
*
*** PSYBK - Persistent System Permanent Free Storage

PSYBK Cross Reference

Symbol         Dspl Value
-------------- ---- -----
PSYBWD         0004
PSYCHN         0010
PSYCODE        0008
PSYDWUSE       000E
PSYFWD         0000
PSYLEN         0018 00000020
PSYSIZE        0018 00000004
PSYTODST       0018
PSYVMFRG       000C