Many applications use two files on the same volume. A common mistake is to assign the files-thus the volume -to two different devices during the job. Using the DVCVOL JPROC helps to avoid this. This JPROC assigns logicalunitnumbers for the generated DVC job control statements. It also generates a VOL job control statement with the volume serial number you specify in the JPROC call. The format is:
//[symbol) DVCVOL [vo1ser-no [,Lun][NOVOL= y
RES
[
iNIRUN
The symbol in the label field is only used as a target for the job control statement that causes a branch.
The DVCVOL JPROC assigns the logicalunitnumbers 50 through 59, in ascending sequence, to the different volume sequence numbers in the order they are encountered in the control stream. If you had three volumes, A, B, and C, in that sequence, A would be 50, B would be 51,andC would be 52. It is possible, however, to override these volumes and assign a specific logicalunitnumber to a specific volume by using the lun parameter.
The NOVOL parameter (NOVOL=Y) performs the same function as the NOV parameter of the VOL job control statement. It suppresses the checking of volume serial numbers.
Once a logicalunitnumber is assigned by the DVCVOL JPROC call to a ‘‘olume, the same logical unit number is assigned whenever this volume is encountered in the job.
If volume A was assigned 50 in one job step,andyou tried to assign it to 51 in the next job step, the system overrides the 51 and assigns 50.
If you tried to do this by using just the DVC and VOL job control statements,
assigning 50 in the first job step and 51 in the next job step,yourjob may run, but you may have to demount the volume from DVC 50 and mount it on DVC 51.
When you use the DVCVOL JPROC call, the LBLandLFD job control statements for the file must be present in the control stream after the DVCVOL JPROC call. If you’re allocating a file on a disk volume, the EXT job control statement must, of course, also be used.
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There is a limit to the number of volumes you can assign using the DVCVOL JPROC call inajob: 10.
Another point worth remembering: the DVCVOL JPROC callcanbe a member of a multistatement line of coding, but it must be the last statement on the line.
Let’s set up a control stream with some DVCVOL JPROC calls,andsee what job control statements are generated. The numbers refer to the explanation following the example.
/1 DVCVOL DISKØ1 II LBL A
1 II LFD A If DVCVOL DSKØO2 II LBL B If LFD B
2. II DVCVOL DKØOO3,69 II LBL C ii LFD C 3. II DVCVOL DISKØ1
II LBL X II LFD X
4. II DVCVOL DKØOO3,67 //LBLY
II LFD Y
1. This is an example of a multistatement line of coding. Note that the DVCVOL JPROC call is the last statement on the line. The next lineand the line after example 2 are also multistatement lines.
2. This line assigns a specific logicalunitnumber, 69, to the volume DK0003.
()
3. This DVCVOL JPROC call is used again for the volume DISKO1. It was also used in the first DVCVOL JPROC call on the first line. It will be assigned the same logicalunitnumber assigned to the first call for the volume DISKO1. You’ll see this more clearly when we show the job control statements generated by these DVCVOL JPROC calls.
4. This is another example calling for the volume DK0003, which was already assigned a logicalunitby a DVCVOL JPROC call. Notice that it also requests a specific logical unit number: 67. Since this volume already was assigned to logical unit number 69 in example 2, the request for logicalunit number 67 is ignored, and it is assigned to logicalunitnumber 69.
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Here are the generated job control statements. They should give you a clearer picture of how each DVCVOL JPROC call functioned.
1. II DVC 50
1. Volume DISKO1 was the volume encountered in the first DVCVOL JPROC call-it’s assigned to logical unit number 50. The LBL and LFD job control statements are not generated by the JPROC call. Remember, these were supplied in the control stream. If another DVCVOL JPROC call for volume DISKO1 is encountered in this job, it is automatically assigned to logicalunit number 50.
2. A DVCVOL JPROC call for volume DSKOO2 was the next one encountered.
It’s assigned the next available logical unit number. Since 50 was already assigned to volume DISKO1, 51 is the next available logical unitnumber.
3. The next DVCVOL JPROC call was for volume DK0003. Normally, it would be assigned to logicalunitnumber 52, which was the next one available.
But, the DVCVOL JPROC call for this volume requested a specific logical unitnumber, 69, so that’s what is assigned.
4. Another DVCVOL JPROC call for volume DISKO1 was encountered. Since this volume was already requestedandassigned earlier in the control stream, this occurrence is assigned the same logical unit number: 50.
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5. The volume DK0003 was requested by another DVCVOL JPROC call. Even though a specific logical unit number, 67, was requested, it was assigned to logical unit number 69, since this is the logicalunitnumber assigned earlier in the job. The first number encountered is used,and anyother logicalunit numbers requested for the volume in the same job are ignored.
To assign multiple diskette volumes through a JPROC call, use the DVCDKT JPROC.
• It functions the same as the DVCVOL JPROC except that it assigns the logicalunit numbers 130 through 132. Its format is:
//[syrnbol] DVCDKT voi.ser-no[,Lun)FNOVOL=
r’’
L
There is also a JPROC call for tape units: DVCVTP. Except for a few minor
differences, it functions the same as the DVCVOL and DVCDKT JPROCS. Its format is:
Illsymbol) DVCVTP vol.ser.noEftun][PREP= {Y}1 [NovOL=
ç}
The DVCVTP JPROC call assigns the logicalunitnumbers 90 through 99.
Additionally, DVCVTP has the keyword parameter PREP=Y. If specified, this parameter functions the same as the PREP option of the VOL job control statement (“Ignoring or Changing the Volume Serial Number” in Section 4); it causes any information currently on the tape volume to be effectively erased.