Type ASSEMBLE
Source Lines : 513
Fixes Applied : 6
Most Recent Version : Tuesday, December 12, 1978
Last Fix ID : [R15172DS]

Module

       DMSSBS (DMSSBS - BASIC SEQUENTIAL ACCESS METHOD)

Function

       THE CMS  BSAM ROUTINE  PROCESSES SEQUENTIAL  READ AND
       WRITE MACROES.

Attributes

       REENTRANT, NUCLEUS RESIDENT

Operation

       THE CMS BSAM ROUTINE IS CALLED BY AN OS READ OR WRITE
       MACRO.  IT CHECKS DCBFDAD TO SEE IF THE FIRST BYTE IS
       A P.   IF SO, THE CONTENTS  OF THE LAST TWO  BYTES OF
       DCBFDAD ARE INCREMENTED BY ONE AND STORED IN FCBITEM.
       IF P IS SPECIFIED AND THE DEVICE IS A TAPE, DMSTIO
       IS USED TO BACKSPACE OR FORWARD SPACE TO THE SPECIFIED
       ITEM. NEXT THE FCB DUMMY OPTION IS CHECKED. IF IT
       IS SPECIFIED, HEX '4200000C' (EOF ERROR) OR HEX '7F000000'
       (NO ERROR) IS STORED IN THE ECB, DEPENDING ON WHETHER A
       READ OR WRITE WAS ISSUED, AND CONTROL IS RETURNED TO THE
       USER. IF THE FCB DUMMY OPTION IS NOT SPECIFIED, THE
        DSORG OPTION IS CHECKED.

        .  IF THE  DSORG OPTION  IN  THE DCB  IS DA  (DIRECT
       ACCESS), CONTROL IS GIVEN TO THE
       DMSSBD ROUTINE TO
       CONVERT THE RECORD IDENTIFICATION INTO AN ITEM NUMBER
       AND PROCESS
       ANY  KEYS USED.   IF  DMSSBD COMPLETES  SUCCESSFULLY,
       CONTROL IS RETURNED TO DMSSBS.
       OTHERWISE, CONTROL IS RETURNED TO THE USER WITH AN
       ERROR CODE.

        . IF THE DSORG OPTION IN  THE DCB IS PO (PARTITIONED
       ORGANIZATION) AND A WRITE IS SPECIFIED AND THE FCBPDS
       ENTRY  IS ZERO,  CONTROL  IS  PASSED TO  THE  PDSSAVE
       ROUTINE
       IN DMSSVT
       TO SAVE  THE DIRECTORY OF  THE PDS  (PARTITIONED DATA
       SET) AND  POINT THE  FCB FILE ITEM  NUMBER TO  A FREE
       MEMBER  SLOT.   IF  PDSSAVE  COMPLETES  SUCCESSFULLY,
       CONTROL IS RETURNED TO DMSSBS.  OTHERWISE, CONTROL IS
       RETURNED TO THE USER WITH AN ERROR CODE.

        . IF  THE DSORG  OPTION IN THE  DCB IS  PS (PHYSICAL
       SEQUENTIAL) AND THE MACRF OPTION IS WL (CREATE A BDAM
       DATA SET)*,  AN EIGHT  IS PUT  IN REGISTER  15 AND  A
       CHECK  IS MADE  TO  SEE IF  END  OF  EXTENT HAS  BEEN
       REACHED.  IF SO, CONTROL IS  RETURNED TO THE USER. IF
       NOT, REGISTER 15  IS SET TO ZERO AND A  CHECK IS MADE
       OF THE  OPTION SPECIFIED IN  THE WRITE  MACRO'S DECB.
       IF SZ IS SPECIFIED AND THE KEYLENGTH IS ZERO,
       CONTROL IS RETURNED TO THE USER WITH A HEX '7F'
       IN THE ECB. IF SD OR SZ IS SPECIFIED AND THE
       KEYLENGTH IS NONZERO, DMSSBD IS CALLED TO WRITE
       256 DUMMY KEYS AND
       UPON RETURN FROM DMSSBD CONTROL IS PASSED BACK
       TO THE  USER WITH A  HEX '7F' IN  THE ECB.  IF  SD IS
       IS SPECIFIED AND THE KEYLENGTH IS ZERO, A KEY OF X'FF' IS
       PUT IN THE DATA AREA AND DMSSBS PROCESSES THE DATA AS A
       NORMAL WRITE. IF SF IS
       SPECIFIED, A HEX '7F' IS STORED IN THE ECB AND IF THE
       KEYLENGTH IS NOT ZERO
       DMSSBD IS  CALLED TO  PROCESS A  KEY.  IF  THE DMSSBD
       ROUTINE
       AND/OR  THE  CHECK  FOR VALID  OPTIONS  IS  COMPLETED
       SUCCESSFULLY DMSSBS BEGINS FILLING IN THE IOB AND THE
       I/O PLIST. OTHERWISE CONTROL IS RETURNED TO THE
       USER WITH A HEX '42' IN THE ECB, DENOTING AN ERROR.

        . IF THE DSORG OPTION IN  THE  DCB IS PS OR PO AND A
       NONZERO KEYLENGTH IS SPECIFIED AND THE MACRF OPTION IS
       NOT WL, DMSSBD IS CALLED TO READ OR WRITE A KEY.  IF
       DMSSBD COMPLETES SUCCESSFULLY, DMSSBS BEGINS FILLING
       IN THE I/O PLIST. IF NOT, CONTROL IS RETURNED TO
       THE USER WITH A HEX '42' IN THE ECB.

        . AFTER THE NECESSARY CHECKS AND CALLS FROM DMSSBD
       AND PDSSAVE  ARE MADE, DMSSBS  FILLS IN  THE IOBIOFLG
       BIT, THE  IOTYPE BYTE, THE  DCBOFLGS BIT,  THE BUFFER
       LENGTH, THE BUFFER
       ADDRESS, THE DECB I/O STARTED BIT, THE IOB POINTER IN
       THE DECB AND THE ECB POINTER IN THE IOB.
       CONTROL IS THEN PASSED TO THE DMSSEB ROUTINE TO DO
       THE I/O AND FILL IN THE ECB.
       AFTER CONTROL IS PASSED BACK TO DMSSBS FROM DMSSEB,
       CONTROL IS PASSED BACK TO THE USER.

       *  IF THE  WL  (CREATE A  BDAM  DATA  SET) OPTION  IS
          SPECIFIED, THE NUMBER  OF RECORDS IN THE  DATA SET
          EXTENT  MUST   BE  SPECIFIED  USING   THE  FILEDEF
          COMMAND.  THE DEFAULT SIZE IS 50 RECORDS.

Calls to Other Routines

       DMSSBD, DMSSVT, DMSSEB, DMSTIO