What does IMS High Performance Load do?
IMS™ High Performance Load consists of the IMS HP Load utility, the Physical Sequence Sort for Reload utility, and the Bitmap Resetter utility. It also provides the Load application programming interface (Load API).
- IMS HP Load utility
- The IMS HP Load utility provides high performance reload processing for databases. The utility is a performance replacement of the IMS HD Reorganization Reload utility (DFSURGL0). The IMS HP Load utility supports various database organizations. It creates the indirect list data set (ILDS) of a HALDB that is compatible with the one created by IMS standard IMS HD Reorganization Reload utility. Also, the utility provides reports that contain statistics about space use and segment pointers.
- Load API (application programming interface)
- IMS High Performance Load provides the Load application programming interface (Load API). By using the Load API, you can run the initial load process much faster than that of IMS DL/I.
- Physical Sequence Sort for Reload utility
- The Physical Sequence Sort for Reload utility sorts an unloaded database data set that is produced for an HDAM database to reduce the elapsed time that is required to reload the database. It also sorts an unloaded database data set for an HDAM, a PHDAM, a HIDAM, a PHIDAM, a HISAM, or a SHISAM database. When you change the partition selection method of a HALDB, Physical Sequence Sort for Reload is required before you reload the HALDB by using IMS HP Load. The utility also provides reports, for use in the tuning analysis of the randomizing parameters.
- Bitmap Resetter utility
- The Bitmap Resetter utility can be used to adjust the bitmap of an HDAM, HIDAM, PHDAM, or PHIDAM database to accommodate denser packing of the database blocks.
The following subsections describe the program functions of the IMS HP Load utility.
- Reloading IMS databases by using high performance methods
- Initializing an empty database
- Providing a user exit facility for additional processing of each segment
- Generating statistics reports to aid in tuning the database
Reloading IMS databases by using high performance methods
IMS HP Load performs high-performance reloading of IMS databases from an HD unloaded data set that is created by:
- Unload utilities of IMS High Performance Unload for z/OS®
- IPR Unload utility of IMS Database Reorganization Expert for z/OS (formerly known as IMS Parallel Reorganization for z/OS)
- IMS HD Reorganization Unload utility (DFSURGU0)
You can use this utility to increase the efficiency of the database reorganization process.
When you use IMS HP Load to reload a HALDB, the partition data set of that HALDB does not need to be initialized. You can skip the step before you run IMS HP Load, by specifying the PARTINIT=YES statement in the FRRIN data set. IMS HP Load itself performs the required partition initialization.
Optionally, IMS HP Load can reload an HD unloaded database data set with compressed segments, created by the IMS High Performance Unload for z/OS unload utilities or by other compatible utilities, in a compressed form without calling the segment compression routine. In this case, the segment compression routine must not be changed during the reorganization. IBM® IMS Library Integrity Utilities for z/OS can be used to detect such a change. If it detects the change and the input unloaded data set is in a compressed form, the reload job ends abnormally. For information about IMS Library Integrity Utilities, see the IMS Library Integrity Utilities User's Guide.
IMS HP Load supports logical relationships and secondary indexes. Logical relationships and secondary indexes of HALDB databases are also supported.
IMS HP Load supports the IMS DBRC feature.
Initializing an empty database
If you specify the DFSUINPT DD DUMMY statement, HDAM and HIDAM databases are initialized.
If you specify the DFSUINPT DD DUMMY statement and the PARTINIT=YES control statement, and also if the partition initialization flag is on for the partition to initialize, PHDAM and PHIDAM databases are initialized.
For an HDAM database and each partition of a PHDAM database, the entire root addressable area is preformatted.
An HIDAM and each partition in a PHIDAM database contains a root segment with a key of all X'FF'.
Providing a user exit facility for additional processing of each segment
IMS HP Load supports a user exit routine. IMS HP Load invokes the user exit routine to exercise additional selectivity or modification of segments to be received from the HD unloaded data set.
Generating statistics reports to aid in tuning the database
IMS HP Load generates statistics reports about data sets, segments, and segment pointers. The reports serve as a valuable aid in tuning the database.