IMS system generation macros used by DBCTL

The first macro in a DBCTL system generation is IMSCTRL. It is always required and there can be only one in each IMS system definition. IMSCTRL describes the MVS™ system under which IMS executes, the type of IMS system, the type of generation to be performed, and the components of the IMS environment, for example, IRLM and DBRC. Because DBRC is mandatory for DBCTL, you do not need to specify the IMSCTRL parameter, DBRC=YES. (If you do specify this parameter, it is ignored.) You can use IMSCTRL to cause the IMS nucleus and the DDIR and PDIR to be regenerated.

MAXREGN is the number of regions (threads) that DBCTL allocates at startup. MAXREGN takes a value 1 - 999. It can increase dynamically to a maximum of 999. Each BMP needs one region. Each connected CICS® needs from MINTHRD to MAXTHRD regions. See also MINTHRD and MAXTHRD, which are used to specify the minimum and maximum numbers of threads for a particular CICS system, as described in Defining the IMS DRA startup parameter table. For information about how these parameters interact, see Specifying numbers of threads. (MAXREGN is not the only parameter you need in IMSCTRL, but is mentioned here to contrast it with MINTHRD and MAXTHRD.)

You use the APPLCTN macro to name PSBs (one macro for each PSB) that application programs use to access databases through DBCTL.

If multiple CICS transactions or BMPs are to schedule a PSB concurrently, the APPLCTN macro for that PSB must specify SCHDTYP=PARALLEL. If you do not specify SCHDTYP=PARALLEL, only one transaction at a time can schedule a PSB. You can change the SCHDTYP of a PSB using the online change process and the /MODIFY command, which you enter at the DBCTL console. See Changing DBCTL resources online for more information about the online change process and the /MODIFY command.

In DBCTL, PSBs used by CICS transactions can be defined with either the TP option or the BATCH option. In the example in Example of JCL required to generate a basic DBCTL subsystem, the BATCH option is used. This example also includes an example of defining a PSB for the CDBM operator transaction.

You use the BUFPOOLS macro to specify default main storage buffer pool sizes for DBCTL, including the size of the DMB and PSB pools. You can override these values at startup using the CSAPSB=, DLIPSB=, and DMB= parameters.

You use DATABASE macro statements to define the databases that DBCTL accesses (one macro for each database). Each physical database must be referenced on a DATABASE macro statement. You can change this resource through the online change process using the /MODIFY command, which you enter at the DBCTL console. See Changing DBCTL resources online for more information about the /MODIFY command.

The FPCTRL macro statement defines the fast path options when DEDBs are used. You must use this macro only if you want DEDB support.

The IMSCTF macro statement includes parameters to define the SVCs to be used by DBCTL, logging options, and the device type for DBCTL's restart data set.

The SECURITY macro statement enables you to specify optional security features to be in effect during IMS execution, unless they are overridden during system initialization.

If you are implementing IMS security use the Resource Access Control Facility (RACF®), see System administration in IMS product documentation. For more information about security with DBCTL, see Security checking with DBCTL.

The IMSGEN macro statement must be the last system definition macro in the Stage 1 input. It specifies the assembler and linkage editor data sets and options, and the system definition output options and features. It specifies the suffix character for the IMS nucleus (DFSVNUCx in IMS.RESLIB) and for the DDIR (DFSDDIRx) and PDIR (DFSPDIRx) in IMS.MODBLKS. You must specify the MACLIB parameter of the IMSGEN macro as MACLIB=ALL when using DBCTL for the first time.