We understand the IBM guidance on managed ACB(s), therefore our IMS development team has been working extra hard to enable some of our IMS tools for IMS-managed ACB(s). This positions our IMS tools for the future, because customers will be able to use our IMS tools in modern IMS environments. We have just delivered support for IMS-managed ACB(s) for our core IMS tools.
Why do IMS-managed ACB(s) matter?
First things first, IBM provided guidance that IMS management of ACB(s) will be required in the future, although no exact date has been set. We assume the feature is still not mature enough to be made a requirement. Even after announcement, it will be some time before the requirement will be fully “enforced”. Why? It comes down to requirements for process changes that cost time and resources as well as other prerequisites (though we won’t go into all of that here).
For those already familiar with the concepts of the IMS database, you are well aware of the need to create your DBD(s), PSB(s) and to ultimately join that information in ACB(s). The Database Definition (DBD) defines the IMS database. The Program Specification Block (PSB) defines the program(s) that will access the specified database. The ACB (Application Control Block) is a kind of merge of the DBD and PSB. Upon defining these elements, you still need to “do a gen”, i.e. DBDGEN, PSBGEN and ACBGEN. Upon completion, you are left with all the libraries. Let’s call this an ‘old’ environment. Should you decide to go ‘modern’, you’ll still have all your old libs to deal with, but you can use IBM’s DFS3UACB utility to populate the IMS catalog (see below).
What are the advantages of IMS-managed ACB(s)?
- There are several benefits in using IMS-managed ACB(s), and we assume these are the most important:
IMS specialists can create, alter and delete databases in a more effective and modern way, i.e., in the same manner as you do with Db2 and other relational databases, as well as the programs that access them. This is achieved through the use of SQL DDL. Knowledge of ACBs, PSBs, DBDs, and all the related GENs are no longer needed. Alternatively, IMS specialists can use IMS generation utilities.
- IMS environments will no longer contain DBD, PSB and ACB libraries since the IMS catalog and IMS directory will be the one-and-only source for metadata about IMS databases and applications. Again, this concept is very similar to that employed in the Db2 world, plus it will be easier to get information about your IMS DBs using tools such as IMS Explorer. To access the IMS catalog using modern database management tools, you must have JDBC drivers in place, otherwise you can use a GUR DLI call.
- The two points above make it clear that IMS has been modernized and IBM has been trying to make things simpler for the new generation of Mainframers, which – in my opinion – may one day result in a near indifference to the type of database used (maybe that’s a bit of a stretch, but all things being equal, database professionals will decide which DB to use based on its strengths and the purposes served.)
Which products are enabled for IMS-managed ACB(s)?
To create the proper IMS environment for our tools, you can use the DFS3CDX0 IMS Catalog Definition user exit routine. Another option is to specify the DFSDF= parameter in SYSIN or the product PARMLIB.
The following core IMS tools products and functions support IMS-managed ACB(s):
UNLOAD, RELOAD, FORMAT,RESETBITMAP, EXTRACT, PFXRES, PFXUPD, PFXRESUPD
ANALYZE/ANALYZEALL, DISASSEMBLE, DISPLAY, ZAP
- High Performance Recovery (HPR)
RECOVER, CHACCUM
COPY, ACOPY, COPYIC
- Secondary Index Builder (SIB)
INDEXCREATE, INDEXEXTRACT, INDEXBUILD
- Program Restart Manager for IMS (PRM)
Documentation:
http://techdocs.broadcom.com/content/broadcom/techdocs/us/en/ca-mainframe-software/database-management/ca-database-management-solutions-for-ims-for-z-os/20/getting-started/ims-managed-application-control-block-acb-support.html
PTFs:
SO12845 and its pre-requisite as well as dependent PTFs
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