IMS Database Recovery Facility address space considerations

IMS Database Recovery Facility runs in a multiple address space environment. The main job can be submitted by the user or a job scheduler, or initiated as a started task.

The job name is determined by the user. The authority is obtained from the user ID that is associated with the job.

For database recovery processing, IMS Database Recovery Facility initiates a master address space that initiates one or more recovery sort subordinate address spaces. When any of the integrated auxiliary utilities are invoked during database recovery, IMS Database Recovery Facility also initiates one or more utility address spaces to perform the processing that is associated with that utility. The address spaces that can be directly initiated by IMS Database Recovery Facility are described in the following list. Table 1 provides details about the name and characteristics of each of these address spaces. All address spaces are initiated as started tasks.

IMS Database Recovery Facility master address space: This address space is the main address space, which controls the processing and functions that are being performed in the recovery job. It reads the necessary logs and change accumulation data sets and controls the initialization and termination of the subordinate address spaces.
Recovery Sort Subordinate address space: This address space processes and sorts log and change accumulation records and restores image copy data. It also provides the API that is necessary to invoke the services of IMS High Performance Image Copy and IMS High Performance Fast Path Utilities (DEDB pointer checker). Multiple recovery sort address spaces can be initiated.
Index Builder Utility address space: This address space is used to perform the processing that is associated with the IMS Index Builder. It rebuilds the non-HALDB primary and all secondary indexes for a database and initiates IMS Index Builder address spaces. Multiple Index Builder Utility address spaces can be initiated.
DFSPREC0 Utility address space: This address space is used to perform the processing that is associated with the IMS HALDB DFSPREC0 utility. It rebuilds the HALDB Primary Index data set and Index List data set. Multiple DFSPREC0 Utility address spaces can be initiated.
Pointer Check Utility address space: This address space is used to perform the processing that is associated with the IMS High Performance Pointer Checker (full-function pointer checker). Only a single Pointer Checker Utility address space is initiated.

The following table describes the subordinate address spaces that can be directly initiated by the IMS Database Recovery Facility. It shows how the name is determined, how many address spaces can be started, and which JCL procedure is used to build the JCL.

Table 1. IMS Database Recovery Facility address space characteristics
Address space	Started task control (STC) name	Number started	JCL procedure used
IMS Database Recovery Facility master address space	Determined by the name on the job card	One master address space per recovery job	A default FRXMAS procedure is supplied.
Recovery Sort subordinate address space	DRFSORT if ASGNAME(Y) ASPREF() prefix if ASGNAME(N)	The actual number is determined by the number of DBDSs that are being recovered and input image copies. The number is limited by the SORTPARM (NUM(x)) value.	The JCL procedure is specified by the DRFPROC() value. The default is FRXJCLSB.
Index Builder Utility address space	IBPREF() prefix The default prefix is BDRF	One for each index that is being rebuilt	The JCL procedure is specified by the DRFIAX() value. The default is FRXJCLIP.
DFSPREC0 Utility address space	PRPREF() prefix The default prefix is PDRF	One for each PHIDAM primary index or ILDS data set rebuilt	The JCL procedure is specified by the DRFIAX() value. The default is FRXJCLIP.
Pointer Checker Utility address space	PCPREF() prefix or PCJOBNM() value The default is FABPATH0	One, regardless of the number of DBDs that are being checked.	The JCL procedure is specified by the PCPROCNM() value. If PCPREF() or PCJOBNM() is specified, FABPATHZ is used.

For more information about the listed parameters, see the IMS Recovery Solution Pack: IMS Database Recovery Facility User's Guide.

For more information about configuring HD Pointer Checker, see Configuring HD Pointer Checker to use with IMS Database Recovery Facility.

All started tasks that are created by IMS Database Recovery Facility run with the same authority as the main job that was initiated. When IMS Database Recovery Facility initiates a started task, the code that is running in that address space creates a security control block that matches the one that is associated with the main job. This control block is swapped in the new address space so that it has the same level of authority as the main job. However, for a short period of time, the started task is running with default authority.

For details about this situation and potential problems, see RACF considerations for subordinate address spaces.