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The SYS-ED knowledge base is a service for answering questions, inclusive of the research and validation of the accuracy of information in the public domain. Citation of source documentation and examples are used to provide answers to the questions. Utilization of this service and reliance on the answers, information, or other materials received through this website is done at your own risk.

Q I am a recent college graduate and everything in the IMS mainframe world is new to me: terminology, acronyms, and computing logic. I have had my own personal computer since I was 10 years of age and I have written programs in Pascal and Visual Basic. Could you provide me with a quick list of IMS structure and acronyms?
A

Some people would say that a computer is a computer and all computing is the same - PC or mainframe. However; the terminology is quite different. This table should be helpful:

MPP Message Processing Program MPP handles online processing with a DL/1 Interface. The input is from message queues.
JMP Java Message Processing Program Similar to MPP except only Java applications can be scheduled.
IFP Fast Path Program IFP handles online processing with a DL/1 interface. The input is from an Expedited Message Handler.
BMP Batch Message Processing Handles batch processing with a DL/1 interface. The IMS Job Management Controlled Execution handles execution of the components.
JBP Java Batch Message Processing Similar to non-message driven BMP except only Java applications can be scheduled.

Q We are a large DB2 and Oracle shop; however we also have to maintain/update IMS applications written in the 1980s. Can DB2 be accessed from an IMS Application?
A Yes. DB2 can be accessed from an IMS application and there are several advantages in doing so.

The IMS TM strengths can be leveraged for accessing DB2 data:

  • By taking advantage of the high system availability of IMS architecture.
  • By using multiple access pathways from IMS transactions, IMS BMP region and IMS Batch.

Q I have been working with IMS since the mid 1990ís as an application programmer and I am now responsible for the database administration and recovery responsibilities. How important is DBRC and will there be many changes in IMS V8?

A

Database Recovery Control - DBRC will be an integral part of your job responsibilities.

The DBRC RECON record is now a maximum of 16MB. These large maximum record sizes are needed to extend IMS continuous availability. IMS V8 uses "segmented" records instead of VSAM spanned records. It is not limited by VSAM maximum record size or control area size. The maximum total size of all segments is also 16MB.


Q

What is meant by IMS Transaction Flow?

A IMS Transaction flow is considered to be comprised of three stages:

Stage 1: Application Program Processing

Stage 2: Normal Transaction Termination

Stage 3: IMS Output Message Process

The transaction flow within each of the three stages are:

Application Program Processing
1 - Initialization 2 - Obtain Message 3 - Database Call(s)
4 - Changes Logged 5 - Message Request(s) 6 - Output Messages(s) Logged
7 - Obtain Next Message 8 - Queue Output to Destination 9 - Database Write(s)
10 - Sync-Point Logged

Note 7 - is optional.

Normal Transaction Termination
1 - Sync-Point 2 - Queue Output to Destination(s) 3 - Database Write(s)
4 - Termination Logged

IMS Output Message Process
1 - Take Message from Message Queue 2 - MFS Formatting 3 - Send Message to Terminal
4 - Send Completion Logged

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