Assessing application changes
Because the design and tuning of an existing production IMS online system involves many people and much machine time, you need to minimize the impact of a change and identify as many potential ramifications as possible.
The following table summarizes how a change in an application program (or your control of the system) can be assessed for impact. It shows the IMS area affected and suggests what other administrative areas of responsibility might be affected.
If you are notified of an application program design change or are tracking a staged implementation, you must extract from the documentation the necessary physical system definition changes. You also need suitable detail to enable you to assess whether your defined environment and operational control are affected.
The first column of the table shows the kind of change and the second column shows the change event you isolate from the documentation. For example, an application system adds a batch message program to generate a report after closedown of a physical part of the network. The following information can be obtained:
- Programs
- Name and PSB, program size, and use of overlay
- Databases
- Already defined, read-only access
- Transactions
- None
- Message formats
- None
- Output
- Name of spooled output procedure
- Terminals
- None
- Network Control
- Whether any change in network availability
- Scheduling
- BMP region: time, frequency, limits
- Exit routines
- None
- Tuning
- N/A
- Security
- No RAS control
Working with this information, you define the APPLCTN macro, perform system definition (CTLBLKS), and tailor the BMP region JCL. Then you add its BMP scheduling instructions to the operations procedure, including a spooled output print step. Alternative strategies can be to perform a MODBLKS system definition and use online change for the cutover to production mode or to use the dynamic resource definition function.
| Change type | Change event | Areas affected | Impact and actions |
|---|---|---|---|
| Programs | Coding fix | IMS.PGMLIB | Documentation, log the change |
| Database access | IMS.PGMLIB IMS.PSBLIB IMS.ACBLIB | Monitoring DL/I calls and using online change | |
| Addition | IMS.PGMLIB IMS.PSBLIB IMS.ACBLIB APPLCTN macro | Pools and resource contention, and using online change | |
| Databases | Access | IMS.ACBLIB | Monitoring |
| Structure | IMS.ACBLIB | Database reorganization | |
| Additions | JCL, IMS.ACBLIB DATABASE macro | Operations and recovery procedures, and using online change | |
| Transactions | Change content | TRANSACT macro | Recalculate message queues, monitoring |
| Added | TRANSACT macro | Scheduling algorithm, use of online change | |
| Workload | Message Queues | Recalculate blocking | |
| Message formats | IMS.FORMAT | Buffers and monitoring, and using online change | |
| Output | z/OS® file | JCL for devices | Operation procedures |
| Spool print | LINEGRP, LINE macros | Operation procedures | |
| LTERM | TERMINAL macro | Alternative destinations, operational changes | |
| Terminals | VTAM® | System definition macros | VTAM generation, operating procedures |
| ETO | IMS.PROCLIB | ETO generation | |
| Other | System definition macros | JCL for online, operating procedures | |
| Network control | System definition macros | VTAM initialization, MTO procedures | |
| Scheduling | TRANSACT macro | Message class algorithms operating procedures | |
| Exit routines | DL/I | IMS.SDFSRESL | Monitor DL/I calls |
| Message edit | IMS.USERLIB | Ensure against abnormal termination | |
| Security | IMS.USERLIB | Ensure security needs are met | |
| ETO | IMS.SDFSRESL | Monitor ETO | |
| User descriptors | IMS.PROCLIB | ||
| Tuning | JCL parameters | IMS.PROCLIB | Coordinate operators change |
| Security | EXEC parameters | Coordinate operations | |
| IMS.PROCLIB parameters | DFSDCxxx | Coordinate operations | |
| Signon | RACF®, exit routines | Validate passwords and coordinate with nucleus | |
| Terminal | RACF, exit routines | Validate passwords and coordinate with nucleus | |
| Transaction | RACF, exit routines | Validate passwords and coordinate with nucleus | |
| RAS | RACF and exit routines | Validate passwords and coordinate with nucleus |
Related reading: For more information about using DRD commands,
see The dynamic resource definition process
in IMS
Version 15.2 System Definition.