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.