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About importing copybook definitions using the DECODE command

You can use the DECODE command to import copybook definitions while decoding DBD blocks in order to inform IMS about field layouts that were previously known only to an application. This can be useful to incorporate COBOL record layouts into the IMS Catalog so that they can be accessed by the Java programs by name.

Related topic

Using


The DECODE command uses the following DD statements when the value of the IMPORT keyword is Y, that is, IMPORT(Y).

IXPC1

DD (required)

These are the COBOL and/or PL/I copybook libraries to use.

IXPFD     

DD (optional)

This is the Fileaid for the IMS XREF dataset, which, if present, will be used to map copybook names to various DBD segments.

XREFCTL   

DD (optional)

These are the control statements to map copybook names to the DBD segments or DBD names to xref member names explicitly.

The following scenarios are possible:

  • Default behavior (Neither IXPFD nor XREFCTL DDs are present)

The utility will attempt to find copybook names matching each segment name. If a copybook member is found with the same name as the segment, it will be used to generate FIELDs in that segment. Any existing FIELDs already in the DBD will remain intact.

  • Using Fileaid XREF members (IXPFD DD present with no XREFCTL DD)

The utility will attempt to find an XREF member in IXPFD with the same name as a DBD. If such a member is found, the copybooks to use for each segment will be taken from the XREF member.

  • Using explicit mapping only. (XREFCTL DD present with no IXPFD DD)

Control statements in the XREFCTL DD will be used to state exactly which copybook to use for any DBD,SEGMENT pair. These control statements are column independent.

The MAP control card command is used for specifying the copybook to be used as follows:

MAP  dbdname  segname   copybookname

or

MAP  dbdname  segname   copybookname  01-level-name

You must use the control card command MAP to specify that a DBD segment should import a given copybook name. In the example of the control statement above:


    • dbdname - The name of the DBD that contains the segment of interest.
    • segname - The name of the segment to map to a copybook.
    • copybookname - The name of the copybook to use for this DBD segment.
    • 01-level-name - (optional) The name of a top-level qualifier within the copybook to use in order to limit the fields to a specific block in the copybook. If this is not specified, the entire copybook will be used.
Example
//XREFCTL DD *
   MAP  MYDBD    MYSEG1    SEG1CPY
   MAP  MYDBD    MYSEG2    SEG2CPY
   MAP  MYDBD    MYSEG3    SEG3CPY
  • Using xref and explicit mapping. (Both XREFCTL DD and IXPFD DD present)

It is possible to include information for multiple DBD XREFs in one Fileaid XREF member. To indicate which IXPFD member to use for a given DBD, an XREF command must be used in the XREFCTL statements.

The XREF command is column independent and is used as follows::

XREF dbdname  xrefname

In the example of the XREF command above:


    • XREF - The command indicating this is a DBD to XREF member mapping statement.
    • dbdname - The name of the DBD to map.
    • xrefname - The name of the XREF member (in IXPFD DD) to use for this DBD.

The following example shows some DBDs with their own XREF and some that belong to the same XREF member.

Example
//XREFCTL DD *
   XREF MYDBD1   MYXREF1
   XREF MYDBD2   MYXREF2
   XREF SMALLDB1 BIGXREF
   XREF SMALLDB2 BIGXREF
   XREF SMALLDB3 BIGXREF
Warning

Notes

  • Any MAP statements in XREFCTL will be honored if present.
  • If no MAP statement is present for a DBD segment, the appropriate IXPFD member will be used.
  • If the IXPFD member is not present or does not contain information for this DBD, then a copybook with the same name as the segment will be searched for. If none of the above yields an existing copybook, no import will take place for the given segment.


Information
Important

For information about using the BATCH DECODE command, see the BMC AMI Database Integrity for IMS online documentation.

 

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