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

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

The primary function of a CA Datacom/DB database system is the ability to store large volumes of tables and rows while providing quick data access and updates capabilities. A unique technique for the CA Datacom site is the ability to make certain data tables memory-resident. The area is copied into memory as the blocks are read (that is, physical I/O) for normal processing. Subsequent read processing that would typically require the area block to be reacquired by physical I/O can be copied back from the block that was stored in the COVERED memory.

Unlike VIRTUAL databases, COVERED databases use memory to save blocks and replace future physical read I/Os, but all updates to the database are still done to the Index and data areas. The memory is allocated when the COVERED specification is encountered. The area in memory is created and as blocks are accessed they are copied into the memory area. The COVERED 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 updates to index or data information is protected by logging and recovery.

Unlike VIRTUAL, the COVERED specification can help any data and index processing where a database has significant physical read activity. In addition, the COVERED specification can be done for the specific Index or data area, allowing you to target only the high-read physical I/O data sets.

Business Value

By specifying certain high-read databases (specifically the Index and data areas) as COVERED, you can remove significant amounts of physical read I/O for that database. By removing a significant amount of the physical I/O for the database, the response time for those database requests is improved and the overall I/O reduced. Reductions in physical I/O can also include reductions in CPU usage.

Additional Considerations

For AD sites, the CA Products that are using the AD repository can recommend that a specific index or data area be COVERED to improve processing performance.

In most sites, there are Index or data areas that have high physical read I/O content. Focus on these areas. To look for particular areas that are candidates, review the PXX summary statistics or the MUF_AREA_STATS dynamic systems table to find the areas with high-read I/O.