The data control block extension (DCBE) provides further processing
options. EXCP supports these options:
- The BLKSIZE parameter when you issue the OPEN and EOV macros.
- The
BLOCKTOKENSIZE parameter to signify that your program is able to handle
a DASD data set that has the large format attribute. The data set
is not necessarily large. If you code BLOCKTOKENSIZE=LARGE, then
it means that your program can handle a data set that exceeds 65535
tracks or might grow above that size. Look for these differences:
- If the data set is a large format data set, the DSCB the DS1LARGE
bit will be on and the two bytes in DS1LSTAR that contain a relative
track number are logically extended with the DS1TTTHI byte. See the
format 1 DSCB description in Format-1 and Format-8 DSCBs.
- The two bytes in each DEBNMTRK field are logically extended by
the DEBNMTRKHI byte. See Control Blocks.
- If your program calls either of the track conversion routines
that CVTPRLTV or CVTPCNVT point to, then your program should use the
+12 entry points instead of the +0 entry points.
If you do not code BLOCKTOKENSIZE=LARGE on the DCBE macro,
then:
- If the OPEN macro option is not INPUT and the data set is large
format, then OPEN will issue a 213-14 ABEND.
- If the OPEN macro option is INPUT and the data set has more than
65535 tracks on the volume, then OPEN will issue a 213-16 ABEND.
- The CAPACITYMODE parameter to write more data on an IBM® 3590 Magnetic Tape Subsystem that emulates
an IBM 3490 when you issue the
OPEN macro.
- The EADSCB=OK parameter to specify that your application
program supports one of the following, as appropriate:
- VTOC that describes a volume supporting extended attribute
DSCBs. (Reading and Modifying a Job File Control Block (RDJFCB Macro) describes how to open a
VTOC.) An extended address volume may have extended attribute DSCBs.
They are format-8 and format-9 DSCBs. If you do not code this option,
the OPEN function will issue ABEND 113-48 and message IEC142I. Code
this option when your application program supports format-8 and format-9
DSCBs.
- A data set that has extended attribute DSCBs, Track addresses
in DSCBs pointed to by a format-8 DSCB may contain cylinder addresses
above 65,520. If you do not code this option, then OPEN issues a
113-44 ABEND and message IEC142I. Code this option
when your application program supports MACRF=E (EXCP) and the data
set has format 8 and 9 DSCBs.
- The EODAD parameter when you issue an EOV macro. If the
DCBEEODAD field has a non-zero value when the system needs to use
it, this value takes precendence over an EODAD specification in the
DCB. See Foundation Block Extension and Common Interface Parameters.
- The LOC parameter when you issue an OPEN macro. To successfully
open a data set that has been allocated with the XTIOT, UCB NOCAPTURE,
or DSAB above the line dynamic allocation options, you must specify
both:
- DCBE option LOC=ANY. The LOC=ANY option is represented by the
DCBELOCANY bit in the DCBE.
- DEVSUPxx parmlib parameter NON_VSAM_XTIOT=YES. The DEVSUPxx parameter
NON_VSAM_XTIOT is represented by DFAXTBAM bit in the DFA as mapped
by IHADFA.
- The SYNC parameter to control buffered tape marks on an IBM 3590 when you issue the OPEN,
EOV, or CLOSE macros.
Note that the DCBE can be above the 16 MB line even though your
user program is running in 24-bit mode. See
z/OS DFSMS Macro Instructions for Data Sets for
more information concerning the DCBE.