In IMS DB, we have an option to choose two accessing-databases- DL/I database and DEDB database.
DL/I is a general access database manager, thus it is suitable for a wide variety of applications. It is also called full function database.
DL/1 databases provide a hierarchically structured database, that can be accessed by record or sequentially, and by other sequences that were planned and provided for when the database was designed. DL/1 databases are limited in size to 4GB or 8GB per data set unless a portioning database product is used.
Obviously, the application area for which the DEDB was originally designed — the management of customer accounts in a retail bank — is an ideal candidate for that database implementation, but it is far from the only one, and some of the more recent additions to the functions of the DEDB (notably VSO, which has been available since IMS/ESA V5) extend the application areas for which you should consider using a DEDB.
DEDBs are particularly suited for use where large databases, or very low processing costs are required, or when particularly high data availability or very high performance is required. DEDBs were originally part of a separately priced, optional feature.
This results in the documentation and code being separate from that for the Full Function (FF) databases.
- DEDB Usages Very large databases
- High availability requirements
- Highly active databases
- Limited data lifetime
- Extreme performance levels
- DEDB: reduced I/O usage
- DEDB: CPU utilization
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