Selecting the appropriate macros to define your system

The following table of macros shows, in order of complexity, which IMS system definition parameters can be modified by type of system definition. You can override some keywords for some macros by specifying certain keyword parameters on the EXEC statement for the IMS, DBC, or DCC procedure, or by modifying the JCL. Other keywords can also be overridden through IMS commands. For further information, see Tailoring the IMS system to your environment or the notes that follow the table.

To use the following table, find the macro-associated keyword and parameter that you want to change. Then scan across the table to find the first column with an X under the system definition types. This identifies the minimum system definition required to change the parameter. If multiple changes are to be made, scan each macro statement on the figure to determine the minimum system definition. When changing operands, make certain the minimum system definition required to update the operand is performed. If you specify a lower level than that indicated in the following table the results are unpredictable.

The JCL column in the table identifies the EXEC parameter, DFSPBIMS keyword, DFSPBDBC keyword, DFSPBDCC keyword, or, IMS command to override the operand in the macro.

Keywords and parameters changed during a MODBLKS system definition can be brought online through a series of /MODIFY operator commands, except as described in the notes that follow the table below.

The CTLBLKS system definition option on the IMSCTRL macro statement can be used only to replace the control blocks of an existing nucleus—that is, a nucleus having the same suffix.

Adding new device support features or options might require a NUCLEUS system definition, because additional modules (for example, the VTAM® terminal COPY option and module DFSCVEQ0) might need to be bound into the nucleus.

Some of the values can be displayed using the /DISPLAY command shown in table notes. The value in the /DISPLAY column is used to qualify the /DISPLAY command as necessary.

Notes to the preceding table:

1. Changes to existing transactions cannot be introduced through a MODBLKS online change if those attributes are changeable by online commands. It is recommended that you enable dynamic resource definition for MODBLKS resources to dynamically update existing transactions. You can use the /ASSIGN or /CHANGE commands to change existing transactions, but the command needs to be reissued after you perform a local online change or a global online change, before the affected transactions are scheduled. Dynamically updating transactions allows you to avoid issuing and then reissuing the /ASSIGN or /CHANGE commands for the existing transactions.
2. Refer to IMS procedure, DBBBATCH procedure, DBC procedure, DCC procedure, and DLIBATCH procedure.
3. This keyword can be changed with any type of system definition except MODBLKS.
4. Adding or deleting VTAM support requires the minimum of an ON-LINE system definition.
5. Adding a user-supplied exit routine, user message table, or the shared printer message router exit routine requires the minimum of a CTLBLKS system definition. The exceptions to this requirement are the ETO, message greeting, and command security exit routines. To remove the use of these exit routines requires a minimum of NUCLEUS system definition. These exit routines are then loaded or deleted during initialization if they are in IMS.SDFSRESL.
6. The ACCESS attribute is used in data sharing and can be dynamically changed with the /START command.
7. ACCESS can be forced to exclusive by specifying DISP=OLD in the database DD statement or in the DFSMDA definition.
8. Although the value for the Type 2 SVC number is changed in the necessary control blocks for all system definition types, only the ON-LINE and ALL types of system definition bind the SVC module into IMS.SDFSRESL with the proper name required for subsequent bind into the operating system libraries.
9. The DBRC= parameter on the IMSCTRL macro is ignored by IMS.
10. For an online system, modifying the IRLM= or IRLMNM= parameters requires a minimum of a CTLBLKS type system definition. A batch system requires a minimum of either a BATCH or an ALL system definition.
11. Generating a system for use in an IMS backup configuration requires a minimum of an ON-LINE system definition.
12. Adding Database Surveyor support to an IMS system initially generated without it can be done in two ways. If done through system definition, either a BATCH system definition (for batch) or an ALL system definition (for both batch and online) must be specified to include Surveyor. Alternatively, in either a batch or online system, the following JCL can be run:

     //LINKSUR  JOB
     //        EXEC PGM=IEWL,REGION=128K,
     //             PARM='NCAL,LET,XREF'
     //SYSPRINT  DD SYSOUT=A
     //LOAD      DD DSNAME=IMS.ADFSLOAD,DISP=SHR
     //SYSLMOD   DD DSNAME=IMS.SDFSRESL,DISP=SHR
     //SYSUT1    DD SPACE=(CYL,(1,1)),UNIT=SYSDA
     //SYSLIN    DD *
      INCLUDE LOAD(DFSPRSUR)
      INCLUDE LOAD(DFSLI000)
      NAME DFSPRSUR(R)           DATABASE SURVEYOR
     /*

13. Change the DD statement.
14. Adding or deleting support for a specific non-ETO terminal type requires a minimum of a NUCLEUS system definition. A minimum of a NUCLEUS system definition is required if the SIZE= or FEAT= parameter is specified for the first time in an existing system or if the values of these parameters are changed. You can use any type of system definition except MODBLKS to add, delete, or change this macro statement.
15. Adding MSC support for the first time or deleting MSC support requires a minimum of an ON-LINE system definition. A physical link change requires a DD statement change.
16. Adding or deleting channel-to-channel support requires a minimum of an ON-LINE system definition. Adding MSC TCP/IP, VTAM, or MTM support requires a minimum of an ON-LINE system definition. Deleting MSC TCP/IP, VTAM, or MTM support requires a minimum of a NUCLEUS system definition.
17. Removing remote LTERM support from an MSC system requires a minimum of a NUCLEUS system definition.
18. MODBLKS system definition cannot be used to add a transaction that is also adding a new user edit routine. MODBLKS system definition cannot be used to change the order of the transactions if user edit routines are specified. The minimum system definition for either of these occurrences is a CTLBLKS system definition.
19. MODBLKS system definition cannot be used to delete a transaction that has a user edit routine if this is the first or only transaction that is using this edit routine. MODBLKS system definition cannot be used to change the order of the transactions if user edit routines are specified. The minimum system definition for either of these occurrences is a CTLBLKS system definition.
20. The command is /DISPLAY TRANSACTION.
21. The command is /DISPLAY POOL xxxx, where xxxx is the indicated parameter.
22. The command is /DISPLAY DATABASE.
23. The command is /DISPLAY ACTIVE.
24. The command is /DISPLAY LINE.
25. The command is /DISPLAY LINK.
26. The command is /DISPLAY LINK xxxx, where xxxx is the indicated parameter.
27. The command is /DISPLAY NODE.
28. The command is /DISPLAY MODE xxxx, where xxxx is the indicated parameter.
29. For batch systems, specify the parameter in the JCL; for online systems, specify the parameter in the DFSRSRxx member.
30. A BATCH or ALL system definition is required for the change to take effect in a batch environment.
31. A database that is defined in an ALL or MODBLKS system definition cannot be converted into a HALDB partition without a cold start of IMS. A cold start is required even if the database is deleted online. After the cold start, the database must be redefined as a HALDB partition.
32. A database that is defined as a HALDB partition to DBRC and IMS cannot be redefined in an ALL or MODBLKS system definition without a cold start of IMS. A cold start is required even if the database is deleted online.
33. The APPLCTN macro is optional in DBCTL, DB/DC, and DCCTL environments. No warning message is issued if the macro is not included in the Stage 1 system definition. If you exclude the APPLCTN macro from your Stage 1 system definition, application programs must then be defined through the dynamic resource definition (DRD) process.
34. The DATABASE macro is optional in DBCTL and DB/DC environments. No warning message is issued if the macro is not included in the Stage 1 system definition. If you exclude the DATABASE macro from your Stage 1 system definition, databases must then be defined through the dynamic resource definition (DRD) process.
35. The RTCODE macro is optional in DB/DC and DCCTL environments. No warning message is issued if the macro is not included in the Stage 1 system definition. If you exclude the RTCODE macro from your Stage 1 system definition, routing codes must then be defined through the dynamic resource definition (DRD) process.
36. The TRANSACT macro is optional in DB/DC and DCCTL environments. No warning message is issued if the macro is not included in the Stage 1 system definition. If you exclude the TRANSACT macro from your Stage 1 system definition, transactions must then be defined through the dynamic resource definition (DRD) process.