The CDBM GROUP command file, DFHDBFK

Before you can use the GROUP command, CDBM requires a file in which all your predefined commands can be stored. This file, DFHDBFK, is the CDBM GROUP command file. It is a VSAM KSDS. The DFHDBFK file is not required until you first attempt to use the /GROUP command. You can use whatever means you prefer to define this file and to maintain its content.

Defining DFHDBFK

To define the file DFHDBFK and optionally to place some of your group definitions in it, use the sample JCL that is described in Defining the CDBM GROUP command data set. The example given there also shows you how to batch load this file if you want to do so. You can load many definitions in this way, or load none.

To use the /GROUP command functions of the CDBM transaction, add the data set name of the group command file to the definition of the DFHDBFK file within the DFHDBCTL group. You can dynamically allocate the data set name to the file by using CEMT. To do this you will need to disable the file first, set the data set name, and then enable the file again. For more information on CEMT, see CEMT - main terminal.

Record layout in DFHDBFK

Each record in the DFHDBFK file may be up to 1428 characters long, as follows:

Field Length Content Description
1 12 Group A 12-character field containing your chosen name for this group. The acceptable characters are A-Z 0-9 $ @ and #. Leading or embedded blanks are not allowed, but trailing blanks are acceptable.
2 10 IMS Command A 10-character field containing any of the IMS command verbs that are valid for CDBM (see Overview of Database Control (DBCTL) for details). Leading or embedded blanks are not allowed, but trailing blanks are acceptable.
3 1406 IMS Command parameters Up to 1406 characters of parameters appropriate to the chosen IMS command verb. (This will often consist of lists of databases.)
Note:
  • The validity of the IMS command verb is not checked by CDBM. Invalid values will be reported by IMS when the command is attempted.
  • Wildcard characters may not be used in the parameters stored in the CDBM Group command file. This is unlike the other functions of the CDBM transaction which permit the use of wildcard characters to describe multiple similarly named databases.

Maintaining the content in DFHDBFK

One method of maintaining the content once the file is defined is provided by CDBM, which offers a Maintenance function for the DFHDBFK file.

If you press the Maintenance key (PF2) on the main CDBM panel, you get the panel shown in Figure 1.

Figure 1. CICS-DBCTL Group Maintenance panel
 CDBM               CICS/DBCTL COMMAND GROUP MAINTENANCE
 _        ACTION      A add  B browse  D delete  R read  U update
 ____________ GROUP         __________ IMS COMMAND
 >                                                                            <
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 F1=Help  F3=Exit  F12=Cancel

The input fields are Action, Group, IMS Command, and IMS Command parameters (between the > < marks). Group, IMS Command and IMS Command parameters are described in Record layout in DFHDBFK.

The Action field accepts one of the following values:
  • A (Add)
    Add a new record to the DFHDBFK file. If the key already exists, the Add fails.
    Note: To Add a record that is very similar to an existing record, but which has a different key, you may find it helpful to Read the existing record, modify the displayed fields, and then Add this new record.
  • B (Browse)

    Displays the contents of the command file, record by record. Specify any key (or none) to indicate where you want the browse to start. Each time you press ENTER, Browse moves on to the next record. At the end of the file you will be prompted to wrap around to the start of the file. You can accept this or not as you prefer. Incomplete keys, and unknown keys are also acceptable as start points. If no key is provided, the browse starts at the first record in the file.

    If you have used Browse to locate a specific record for deletion or for update, remember to use Read before either Delete or Update.

  • D (Delete)

    Delete a record from the DFHDBFK file. A Delete must be immediately preceded by a Read to lock the required record.

  • R (Read)

    Read displays a specific record. Unlike Browse it does not operate on partial, or absent keys, and does not present the next record when you press ENTER.

    Read is required before those actions (Delete and Update) which change an existing record. It locks that record against the possibility of being changed by another operator. This action also serves to help you confirm that the correct record has been selected.

    A lock is released by exiting the CDBM maintenance panel, or by your next CDBM Maintenance action (whether that is the Update or Delete you had contemplated, or something different entirely).

  • U (Update)

    Update a record in the DFHDBFK file. An Update must be immediately preceded by a Read to lock the required record.

    You cannot update the key fields (GROUP and IMS COMMAND).

    Note: Use Add to create a new key.
Note: In the descriptions, Key refers to the 22 characters at the beginning of each record in the DFHDBFK file (namely the GROUP and IMS COMMAND).