DEDB changes
The following are examples of how to handle some common database changes. After each DBD change, you must perform an ACBGEN.
Adding compression to an existing segment type
You can add compression to an existing segment type by specifying COMPRTN in its SEGM statement in the DBD. You can register the segment if you want to change any of the product defaults. Because DATA PACKER/IMS recognizes uncompressed data, you do not have to perform a database change or reorganization, unless you want the segment data compressed immediately rather than as part of normal database updates.
Adding a new, compressed segment to a database
To add a new, compressed segment to a database, add the segment to the DBD and specify the compression exit name. You can register the segment if you want to change any of the product defaults. After you have added the segment to the DBD, perform a database change as described in Step 7.
Changing a compressed segment
You can increase the length of a segment without a database reorganization by changing it in the DBD and performing a DBDGEN, followed by an ACBGEN. The additional segment area is not initialized by DATA PACKER/IMS. If you decrease the segment length, you must perform a database change using expanded data as described in Changing-compression-techniques-for-full-function-databases-by-using-expanded-data.
Using the IBM SDEP Scan utility
Use the following two ways to expand compressed SDEP segments with the IBM SDEP Scan utility:
- Include the SDEP Scan utility keyword EXPANDSEG
Include the ACBLIB statement in the JCL and specify the following control statement for DPK/IMS's exit:
EXIT=DPISDEPAnother way to accomplish this is to use the EXPANDSEG keyword.
To interrogate the expanded SDEP segment with the use of an exit, include a DPISYSIN DD statement:
//DPISYSIN DD *
userexit
/*If the DPISYSIN DD statement is present, userexit will be invoked. userexit is user-defined. Register 6 (R6) will contain one of the following entry codes:
- 4 (segment)
- 12 (initialization)
16 (termination)
- Using the online data extract feature of the BMC Fast Path Online Analyzer/EP product. To expand data when using this feature, specify the EXPAND=YES keyword on the EXTRACT command. For more information, see the Fast Path Online Suite User Guide.
- Using the IBM DEDB Online Data Extract feature in the Fast Path Online Tools function, components of the IMS High Performance Fast Path Utilities. To extract the data when using this feature, include the ACBLIB DD statement in the JCL.