IMS High Performance Unload system structure

Any application program that runs the IMS High Performance Unload's runtime environment and is serviced by HSSR Engine, is called an HSSR application program. Unload utilities FABHURG1 and FABHFSU are HSSR application programs. You can also write your own HSSR application program.

The following figure provides an overview of the structure of IMS High Performance Unload and its data flow.

Figure 1. System structure and data flow
This figure depicts the system structure and data flow of IMS High Performance Unload. The detail of the flow is described in this topic.

IMS High Performance Unload runs in an IMS batch environment. IMS High Performance Unload runtime environment initializer (FABHX034) is invoked first. The initializer gives control to the IMS region controller DFSRRC00, which passes control to the IMS program controller. IMS High Performance Unload program controller is then invoked by the IMS program controller as an IMS batch application program.

The IMS High Performance Unload program controller calls HSSR Engine. HSSR Engine then reads the HSSROPT data set to initialize the call analyzer, call handler, and trace and diagnosis facilities, and reads the HSSRCABP data set to initialize the buffer handler. Call analyzer initializes PCBs that have been specified to be serviced by HSSR Engine. Such PCBs are called HSSR PCBs (for details about HSSR PCB, see Application programming interface for using HSSR Engine). Call analyzer also initializes control blocks relating to the HSSR PCBs. Buffer handler allocates a buffer pool for each data set group for each HSSR PCB.

The IMS High Performance Unload program controller loads the application program. Each DL/I call or EXEC DLI command to an HSSR PCB is processed by HSSR Engine. This call or command is called an HSSR call. If the PCB is not an HSSR PCB, HSSR call router passes control to the DL/I program request handler.

After the application program runs, it returns control to the IMS High Performance Unload program controller. HSSR Engine terminates the processing and writes statistical reports to the HSSRSTAT data set. Then the program controller returns control to IMS.

For details about each component of IMS High Performance Unload, see the following topics: To run these unload utilities or to use HSSR engine with your application program, you must prepare basic JCL. For information, see Basic job control language.