Configuration Best Practices › Using Memory Resident Data Facility VIRTUAL Index and Data Areas to Reduce Physical I/O Processing

Using Memory Resident Data Facility VIRTUAL Index and Data Areas to Reduce Physical I/O Processing

The primary function of a CA Datacom/DB database system is to store large volumes of tables and rows while providing quick data access and update capabilities. A unique technique for the CA Datacom site is the ability to make certain data tables completely memory-resident, using the Memory Resident Data Facility (MRDF). That is, the areas in the database are created in memory when the VIRTUAL specification is encountered. The areas in memory are created as an empty Index or data areas. All activity is processed only in memory tables, completely removing all I/O. The VIRTUAL definition can be done at MUF startup (recommended) or can be added while MUF is active for databases that are currently not open to MUF. All index or data information is lost when the MUF abends. Only use VIRTUAL specifications for index and data entries that are considered temporary in nature. These are system work data sets. Few CA Datacom/DB databases qualify for this type of processing. When specifying a database as VIRTUAL, all Index and data areas must reside in VIRTUAL storage.

Business Value

By specifying certain temporary databases as VIRTUAL, you completely remove the physical I/O for those databases. By removing the physical I/O for a database, the response time for requests in that database is improved and the overall I/O is reduced. Reductions in physical I/O can also include reductions in CPU usage.

Additional Considerations

The CA Datacom system includes two system databases that are good choices for MRDF VIRTUAL databases:

• The CBS Index database (DBID 006) contains a single Index Area that is used to house temporary indexes created to support CBS (SAAT) requests. Most clients that use the CBS Index find that adding it as a VIRTUAL database improves performance.
• The TTM database (DBID 017) contains an Index Area and a data area used to house temporary tables created to support SQL requests. Most clients that use SQL requests that use the TTM database find that adding it as a VIRTUAL database improves performance.