Defining a Master Catalog

The sample DLBL command used in the preceding example is almost identical with the one you would issue to define a master catalog using AMSERV. The only difference is that you can enter the EXTENT option so you can list the data spaces that this master catalog is to control. As an example, suppose that you have a 30-cylinder 3390 minidisk assigned to you to use for testing your VSAM programs under CMS. If the minidisk is in your directory at address 333, you should first access it:
access 333 d
D (333) R/W - DOS
If you formatted the minidisk yourself, you know what label you assigned it. If not, you can find out the label assigned to the disk by issuing the CMS command:
query search
The response might be:
USR191  191  A    R/W
VSAM03  333  D    R/W - DOS
SYS109  190  S    R/O
SYS19E  19E  Y/S  R/O
Use the volume label VSAM03 in the MASTCAT AMSERV file:
DEFINE MASTERCATALOG -
   (NAME  (MASTCAT ) -
    VOLUME (VSAM03) -
    CYL (4) -
    FILE (IJSYSCT)   )
To find out what extents on the minidisk you can allocate for VSAM, use the LISTDS command with the FREE option:
listds d (free
The response from LISTDS might look like this:
FREESPACE INFORMATION FOR 'D' DISK:
CYL-HEAD    (RELTRK) TO   CYL-HEAD      (RELTRK)      TRACKS
00000 00001        1    00000 00009            9           9
00000 00011       11    00029 00018          569         560
From this response, you can see that the VTOC is located on the first cylinder, so you can allocate cylinders 1 through 29 for VSAM:
dlbl ijsysct d dsn mastcat (perm extent
DMSDLB331R Enter extent specifications:
19 551
    (null line)
After entering the extents, in tracks, giving the relative track number of the first track to be allocated followed by the number of tracks, you must enter a null line to complete the command. (A null line is required because, when you enter multiple extents, entries may be placed on more than one line.)
Now you can issue the AMSERV command:
amserv mastcat
A ready message with no return code indicates that the master catalog is defined. You do not need to reissue the DLBL command to identify the master catalog for additional AMSERV functions.