z/OS DFSMSdfp Advanced Services
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z/OS DFSMSdfp Advanced Services
SC23-6861-01

Use the OBTAIN macro or a CVAF macro.

Start of changeDetermining the Type of Data Set: To learn the type of a data set, test the DS1DSORG field. Except for the DS1DSGU bit, only one bit should be on. If no bit is on, the data set is not standard and the system generally treats it like DSORG=PS. The explanation for all DS1DSORG bits being off might be:
  • The user did not specify the DSORG option and no program has written data in the data set.
  • The data set was created by a program that used EXCP or EXCPVR.
  • The data set was created on another operating system.
All of the above conditions are normal. Normally after a program writes data, the DS1DSORG field will have a bit on. z/OS® currently supports the following types of data set:
  • Physical sequential (DSORG=PS). There are three types:
    • Large format if the DS1LARGE bit is on.
    • Extended format if the DS1STRP bit is on. An indicator in the catalog entry specifies whether it is striped.
    • Basic format if neither of the above two bits is on.
  • Direct (DSORG=DA).
  • Partitioned (DSORG=PO). This can signify one of three types of data set:
    • PDS (partitioned data set) if the DS1PDSE and DS1PDSEX bits are off.
    • PDSE (partitioned data set extended) if the DS1PDSE bit is on and DS1PDSEX bit is off.
    • HFS (hierarchical file system) if the DS1PDSE and DS1PDSEX bits are on.
    Other combinations of these three bits are invalid.
  • VSAM (AMORG). You can use CSI, catalog search interface, to determine the type of VSAM data set. If it is a linear data set, it might contain a DB2® tablespace or a z/OS file system (zFS) or something else.
End of change

Table 1 shows the contents of a format-1 or format-8 DSCB.

The DS1REFD field:
  1. For a VSAM data set, if the date in the FMT-1 DSCB's DS1REFD field is earlier than the current date, OPEN updates the field with the current date.
  2. For a multivolume VSAM data set, OPEN updates the DS1REFD field only for the first volume of the data component of the base cluster.
  3. For a non-VSAM multivolume data set that is not SMS managed, OPEN updates the DS1REFD field on the first volume OPEN selected to use.
  4. For a non-VSAM multivolume SMS-managed data set that is not extended format, OPEN updates the DS1REFD field on the first volume OPEN selected to use, as well as the first volume of the data set.
  5. For an extended format single-striped non-VSAM data set, OPEN updates the DS1REFD field on the first volume OPEN selected to use, as well as the first volume of the data set.
  6. For an extended format multi-striped non-VSAM data set, OPEN updates the DS1REFD fields on all volumes of the data set.
Table 1. DSCB Format-1 or Format-8. DSCB Format-1 or Format-8
Offset Dec (Hex) Type or Bit Mask   Length   Name   Description
0(X'0') Character 44 DS1DSNAM Data set name.
44(X'2C') Character 1 DS1FMTID Format Identifier.
      DS1IDC X'F1'. This is a format-1 DSCB.
      DS8IDC X'F8'. This is a format-8 DSCB.
45(X'2D') Character 6 DS1DSSN Data set serial number (identifies the first or only volume containing the data set/space).
51(X'33') Unsigned 2 DS1VOLSQ Volume sequence number.
53(X'35') Character 3 DS1CREDT Creation date ('YDD'), discontinuous binary. Add 1900 and the value in the Y byte to determine the year. For VSAM data sets that are not SMS-managed, the expiration date is in the catalog.
56(X'38') Character 3 DS1EXPDT Expiration date ('YDD'), discontinuous binary. Add 1900 and the value in the Y byte to determine the year.
59(X'3B') Unsigned 1 DS1NOEPV Number of extents on volume.
60(X'3C') Unsigned 1 DS1NOBDB Number of bytes used in last directory block.
61(X'3D') Bitstring 1 DS1FLAG1 Flags byte
  1 . . . . . . .   DS1COMPR Compressible format data set (DS1STRP is also 1).
  . 1 . . . . . .   DS1CPOIT Checkpointed data set.
  . . 1 . . . . .   DS1EXPBY VSE expiration date specified by retention period (not currently used in z/OS)
  . . . 1 . . . .   DS1RECAL Data set recalled.
  . . . . 1 . . .   DS1LARGE Large format data set.
  . . . . . .11   DS1EATTR Extended attribute setting as specified on the allocation request.(EATTR=)
  • If 0, EATTR has not been specified. For VSAM data sets, the default behavior is equivalent to EATTR=OPT. For non-VSAM data sets, the default behavior is equivalent to EATTR=NO.
  • If 1, EATTR=NO has been specified. The data set cannot have extended attributes (format 8 and 9 DSCBs) or optionally reside in EAS.
  • If 2, EATTR=OPT has been specified. The data set can have extended attributes and optionally reside in EAS. This is the default behavior for VSAM data sets.
  • If 3, Not Used, EATTR treated as not specified.
62(X'3E') Character 13 DS1SYSCD System code.
75(X'4B') Character 3 DS1REFD Date last referenced ('YDD' or zero, if not maintained). Add 1900 and the value in the Y byte to determine the year.
78(X'4E') Bitstring 1 DS1SMSFG System managed storage indicators.
  1 . . . . . . .   DS1SMSDS System managed data set. IEHLIST displays this bit as the letter "S".
  . 1 . . . . . .   DS1SMSUC Uncataloged system managed data set (the VTOC index is an uncataloged system managed data set as are all temporary data sets on system managed volumes). IEHLIST displays this bit as the letter "U".
  . . 1 . . . . .   DS1REBLK System determined the block size and data set can be reblocked (you or the system can reblock the data set). IEHLIST displays this bit as the letter "R".
  . . . 1 . . . .   DS1CRSDB DADSM created original block size and data set has not been opened for output. IEHLIST displays this bit as the letter "B".
  . . . . 1 . . .   DS1PDSE Data set is a PDSE or HFS data set (DS1PDSEX is also 1 for HFS). IEHLIST displays this bit as the letter "I" for a PDSE. IEHLIST displays a "?" when it finds an invalid combination of bits.
  . . . . . 1 . .   DS1STRP Sequential extended-format data set. IEHLIST displays this bit as the letter "E". IEHLIST displays a "?" when it finds an invalid combination of bits.
  . . . . . . 1 .   DS1PDSEX HFS data set (DS1PDSE must also be 1) IEHLIST displays this bit as the letter "H".
  . . . . . . . 1   DS1DSAE Extended attributes exist in the catalog entry.
79(X'4F') Character 3 DS1SCEXT Secondary space extension. Valid only when DS1EXT is on (see offset 94(X'5E')).
79(X'4F') Bitstring 1 DS1SCXTF Secondary space extension flag byte–only one of the first 4 bits is on.
  1 . . . . . . .   DS1SCAVB If 1, DS1SCXTV is the original block length. If 0, DS1SCXTV is the average record length.
  . 1 . . . . . .   DS1SCMB If 1, DS1SCXTV is in megabytes.
  . . 1 . . . . .   DS1SCKB If 1, DS1SCXTV is in kilobytes.
  . . . 1 . . . .   DS1SCUB If 1, DS1SCXTV is in bytes.
  . . . . 1 . . .   DS1SCCP1 If 1, DS1SCXTV has been compacted by a factor of 256.
  . . . . . 1 . .   DS1SCCP2 If 1, DS1SCXTV has been compacted by a factor of 65,536.
80(X'50') Unsigned 2 DS1SCXTV Secondary space extension value for average record length or average block length.
82(X'52') Bitstring 2 DS1DSORG Data set organization.
      First byte of DS1DSORG  
  1000 000x   DS1DSGIS Indexed sequential organization.
  0100 000x   DS1DSGPS Physical sequential organization.
  0010 000x   DS1DSGDA Direct organization.
  0001 000x   DS1DSGCX BTAM or QTAM line group.
  . . . . xx . .     Reserved.
  0000 001x   DS1DSGPO Partitioned organization.
  . . . . . . . 1   DS1DSGU Unmovable; the data contains location dependent information.
      Second byte of DS1DSORG  
  100x 00xx   DS1DSGGS Graphics organization.
  010x 00xx   DS1DSGTX TCAM line group (not supported)
  001x 00xx   DS1DSGTQ TCAM message queue (not supported).
  000x 10xx   DS1ACBM VSAM data set/space.
  000x 10xx   DS1ORGAM VSAM data set/space.
  000x 01xx   DS1DSGTR TCAM 3705 (not supported).
  . . . x . . xx     Reserved.
84(X'54') Character 1 DS1RECFM Record format.
  10 . . . . . .   DS1RECFF Fixed length.
  01 . . . . . .   DS1RECFV Variable length.
  11 . . . . . .   DS1RECFU Undefined length.
  . . 1 . . . . .   DS1RECFT Track overflow. No longer supported by current hardware.
  . . . 1 . . . .   DS1RECFB Blocked; cannot occur with undefined.
  . . . . 1 . . .   DS1RECFS Fixed length: standard blocks; no truncated blocks or unfilled tracks except possible the last block and track. Variable length: spanned records.
  . . . . . 00 .     No control character.
  . . . . . 10 .   DS1RECFA ISO/ANSI control character.
  . . . . . 01 .   DS1RECMC Machine control character.
  . . . . . 11 .     Reserved.
  . . . . . . . x     Reserved.
85(X'55') Character 1 DS1OPTCD Option Code.

BDAM OPTCD field assignments (applies only if DS1DSGDA is on):
  1 . . . . . . .     Write validity check.
  . 1 . . . . . .     Track overflow.
  . . 1 . . . . .     Extended search.
  . . . 1 . . . .     Feedback.
  . . . . 1 . . .     Actual addressing.
  . . . . . 1 . .     Dynamic buffering.
  . . . . . . 1 .     Read exclusive.
  . . . . . . . 1     Relative block addressing.

ISAM OPTCD field assignments (applies only if DS1DSGIS is on):
  1 . . . . . . .     Write validity check.
  . 1 . . . . . .     Accumulate track index entry.
  . . 1 . . . . .     Master indices.
  . . . 1 . . . .     Independent overflow area.
  . . . . 1 . . .     Cylinder overflow area.
  . . . . . 1 . .     Reserved.
  . . . . . . 1 .     Delete option.
  . . . . . . . 1     Reorganization criteria.

BPAM, BSAM, QSAM OPTCD field assignments (applies only if DS1DSGPO or DS1DSGPS is on):
  1 . . . . . . .     Write validity check.
  . 1 . . . . . .     Allow data check (if on printer).
  . . 1 . . . . .     Chained scheduling.
  . . . 1 . . . .     VSE/MVS interchange feature on tape.
  . . . . 1 . . .     Treat EOF as EOV (tape).
  . . . . . 1 . .     Search direct.
  . . . . . . 1 .     User label totaling.
  . . . . . . . 1     Each record contains a table reference character.
85(X'55') Bitstring 1 DS1OPTAM VSAM OPTCD settings.

VSAM OPTCD field assignments (applies only if DS1ORGAM is on):
  1 . . . . . . .     Reserved.
  . 1 . . . . . .   DS1OPTBC Data set is an integrated catalog facility catalog.
  . . xx xxxx     Reserved.
86(X'56') Binary 2 DS1BLKL Block length (Type F unblocked records), or maximum block size (F blocked, U or V records).
88(X'58') Binary 2 DS1LRECL Logical record length: Fixed length-record length, Undefined length-zero, Variable unspanned-maximum record length, Variable spanned and < 32757 bytes-maximum record length, Variable spanned and > 32756 bytes-X'8000'.
90(X'5A') Binary 1 DS1KEYL Key length ( 0 to 255).
91(X'5B') Binary 2 DS1RKP Relative key position.
93(X'5D') Character 1 DS1DSIND Data set indicators.
  1 . . . . . . .   DS1IND80 Last volume containing data in this data set.
  . 1 . . . . . .   DS1IND40 Data set is RACF™, a component of the Security Server for z/OS, defined with a discrete profile.
  . . 1 . . . . .   DS1IND20 Block length is a multiple of 8 bytes.
  . . . 1 . . . .   DS1IND10 Password is required to read or write, or both; see DS1IND04.
  . . . . 1 . . .   DS1IND08 Data set has been modified since last recall.
  . . . . . 1 . .   DS1IND04 If DS1IND10 is 1 and DS1IND04 is 1, password required to write, but not to read. If DS1IND10 is 1 and DS1IND04 is 0, password required both to write and to read.
  . . . . . . 1 .   DS1IND02 Data set opened for other than input since last backup copy made.
      DS1DSCHA Same as DS1IND02.
  . . . . . . . 1   DS1IND01 Secure checkpoint data set.
      DS1CHKPT Same as DS1IND01.
94(X'5E') Binary 4 DS1SCALO Secondary allocation space parameters.
94(X'5E') Character 1 DS1SCAL1 Flag byte.
  xxxx xxxx   DS1DSPAC Space request bits, defined as follows:
  00 . 0 . . . .   DS1DSABS Absolute track request.
  00 . 1 . . . .   DS1EXT Extension to secondary space exists (see DS1SCEXT at offset 79 (X'4F')).
  11 . . . . . .   DS1CYL Cylinder request.
  10 . . . . . .   DS1TRK Track request.
  01 . . . . . x   DS1AVR Average block length request.
  01 . . . . . 1   DS1AVRND Average block and round request.
  . . 1 . . . . .   DS1MSGP Mass storage vol group (MSVGP - no longer supported).
  . . . . 1 . . .   DS1CONTG Contiguous request.
  . . . . . 1 . .   DS1MXIG MXIG request.
  . . . . . . 1 .   DS1ALX ALX request.
  . . . . . . . 1   - Round request.
95(X'5F') Binary 3 DS1SCAL3 Secondary allocation quantity.
98(X'62') Binary 3 DS1LSTAR Last used track and block on track (TTR). Not defined for VSAM, PDSE, HFS and direct (BDAM). See bit DS1LARGE at +61 and byte DS1TTTHI at +104.
101(X'65') Binary 2 DS1TRBAL If not extended format, this is the value from TRKCALC indicating space remaining on last track used. For extended format data sets this is the high order two bytes (TT) of the four-byte last used track number. See DS1LSTAR. Zero for VSAM, PDSE, and HFS.
103(X'67') Character 1   Reserved.
104(X'68') Character 1 DS1TTTHI High order byte of track number in DS1LSTAR. Valid if DS1Large is on.
105(X'69') Character 30 DS1EXNTS Three extent fields.
105(X'69') Character 10 DS1EXT1 First extent description.
  Character 1   Extent type indicator.
  X'81'     Extent on cylinder boundaries.
  X'80'     Extent described is sharing cylinder (no longer supported).
  X'40'     First extent describes the user labels and is not counted in DS1NOEPV.
  X'04'     Index area extent (ISAM).
  X'02'     Overflow area extent (ISAM).
  X'01'     User's data block extent, or a prime area extent (ISAM).
  X'00'     This is not an extent.
    1   Extent sequence number.
    4   Lower limit (CCHH). These are the bit definitions:
0–15
Low order 16 bits of the 28-bit cylinder number.
16-27
High order 12 bits of the 28-bit cylinder number. In a format-1 DSCB, these bits always are zero.
28-31
Track number from 0 to 14. Use the TRKADDR macro or IECTRKAD routine when performing track address calculations.
    4   Upper limit (CCHH). Same format as the lower limit.
115(X'73') Character 10 DS1EXT2 Second extent description.
125(X'7D') Character 10 DS1EXT3 Third extent description.
135(X'87') Character 5 DS1PTRDS In a format-1 DSCB this can be a pointer (CCHHR) to a format-2 or format-3 DSCB or be zero. In a format-8 DSCB this always is the CCHHR of a format-9 DSCB.
140(X'8C') Character   DS1END -
Parent topic: Format-1 and Format-8 DSCBs

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