NAME       : HCPRTHBK
 DESCRIPTION: RECORDING TABLE HEADER BLOCK
 DSECT      : RTHBK
 FUNCTION   : MAPS OUT THE HEADER INFORMATION ON THE RECORDING
              SYSTEM SERVICE TABLE
 LOCATED BY : SYSRECQU
 SERIALIZED : SYSRECLK
 RELOCATION CONSIDERATIONS : None
 COMPATIBILITY AND MIGRATION CONCERNS : This control block gets checkpointed during SHUTDOWN and
              will be read back in during a WARM start.  Therefore, if
              the format of the block changes due to service being
              applied before the warm start, code should be in place to
              distinguish between the old and new format.  (See the
              note below describing the RTHVERS field.)

 RTHBK DSECT
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Hex   Dec Type/Val   Lng Label (dup)    Comments
---- ---- --------- ---- -------------- --------
0000    0 Structure      RTHBK          RECORDING TABLE HEADER BLOCK
0000    0 Signed       4 RTHQUE         ADDRESS OF THE FIRST SYSTEM
                                        RECORD ON THE RECORDING QUEUE.
0004    4 Signed       2 *              RESERVED
0006    6 Signed       2 *              RESERVED. Previously: RTHMSGN
                                        field
      NOTES      : The following field is used to indicate when the RTHBK
            format has changed and what that change was due to.
            Any code defined here should be checked in HCPRECKP
            when old format RTHBK is read from the checkpoint
            cylinders. The old format RTHBK should then be updated
            appropriately to the new format. Code should also be
            added to HCPRIURI to set the code for the RTHBK
            that is being newly created AFTER the format change.
            A new code should only need to be defined
            here when a change to the RTHBK causes it to be
            incompatible with a previous format. Due to
            compatibility, the displacement of the RTHVERS
            field should NEVER change.  Previous versions of this
            control block had this field marked 'RESERVED' and
            the field was known to be zero.  Therefore, previous
            versions were version X'00'.
0008    8 Bitstring    1 RTHVERS        RTHBK Version indicator
          00000000       RTHVN00        X'00' RTHVN00 For version 00,
                                        original format
          00000001       RTHVN01        X'01' RTHVN01 For version 01,
                                        Full Page RTHBK
0009    9 Bitstring    1 RTHRID         RECORDING TABLE IDENTIFIER. SET
                                        TO X'FF' AT INITIALIZATION TIME.
000A   10 Signed       2 RTHFRESZ       RTHBK BLOCK SIZE IN DOUBLE WORDS
000C   12 Bitstring    1 RTHFLAG        RECORDING TABLE FLAGS.
          1... ....      RTHRINIT       X'80' RTHRINIT PURGE IN PROGRESS
          .1.. ....      RTHRINC        X'40' RTHRINC I/O COMPLETE IN
                                        PROGRESS
000D   13 Bitstring    1 *              RESERVED
000E   14 Signed       2 RTHDCNT        LENGTH OF RTHDATA IN BYTES.
                                        RTHDATA IS MAPPED OUT INTO
                                        INDIVIDUAL RECORDING TABLE
                                        ENTRIES WITH THE RECBK DSECT.
0010   16 Character    1 RTHDATA (0)    FIRST RECBK ENTRY IN THE
                                        RECORDING TABLE.
                        COMMON EQUATES
                   OFFSET TO RECBK WORK AREA IN RECORDING TABLE.
          00000FB0       RTHRECWK       (100*RECBLEN)+(RTHDATA-RTHBK)
                                        OFFSET TO RSSBK WORK AREA IN
                                        RECORDING TABLE.
          00000FD8       RTHRSSWK       RTHRECWK+RECBLEN SIZE OF THE
                                        RTHBK (RECORDING TABLE) IN DOUBLE
                                        WORDS
          000001FE       RTHDWRDS       (RTHRSSWK+RSSBLEN+7)/8 SIZE OF
                                        RTHDATA IN BYTES.
          00000FE0       RTHDATAB       (RTHDWRDS*8)-(RTHDATA-RTHBK)

          
*** RTHBK - RECORDING TABLE HEADER BLOCK
*
*     +---------------------------+-------------+-------------+
*   0 |          RTHQUE           |/////////////|/////////////|
*     +------+------+-------------+------+------+-------------+
*   8 |:VERS |RTHRID|  RTHFRESZ   |:FLAG |//////|  RTHDCNT    |
*     +------+------+-------------+------+------+-------------+
*
*** RTHBK - RECORDING TABLE HEADER BLOCK

 
Symbol         Dspl Value
-------------- ---- -----
RTHDATA        0010
RTHDATAB       0010 00000FE0
RTHDCNT        000E
RTHDWRDS       0010 000001FE
RTHFLAG        000C
RTHFRESZ       000A
RTHQUE         0000
RTHRECWK       0010 00000FB0
RTHRID         0009
RTHRINC        000C 40
RTHRINIT       000C 80
RTHRSSWK       0010 00000FD8
RTHVERS        0008
RTHVN00        0008 00000000
RTHVN01        0008 00000001