ResUsage data can help determine cache hit rates by comparing total logical I/O requests to I/O requests that resulted in a physical I/O. Comparing these helps clarify any confusion that may arise when aligning DBQL data with ResUsage data, since DBQL data only tracks logical I/O.
An analogous circumstance occurs when attempting to differentiate between total BYNET message requests and BYNET message requests that result in a physical BYNET message being sent. Smaller systems see a greater difference between the two because of a higher percentage of point-to-point (PTP) messages with the sender and the receiver being the same node.
In ResUsageSpma table, a logical read count, that is, a count of the total number of requested disk segments for the interval, is represented in the FileAcqs column. The physical read count, or the number of requested disk segments that actually resulted in a read by the I/O subsystem, is represented in the AcqReads and the PreReads columns.
There are similar breakdowns for writes. BYNET logical messages are represented in the columns that begin with Msg, and the physical counterparts are represented with the columns that begin with NetMsg.
About Monitoring Memory
Use the ResUsage tables to obtain records of free memory usage and FSG Cache.
| Memory Type | Monitor With | Comments |
|---|---|---|
| Free Memory | ResUsage | See Teradata Vantage™ Resource Usage Macros and Tables, B035-1099 for more information on using ResUsage macros and utilities to monitor free memory and FSG Cache. |
| FSG Cache | ResUsageSpma ResUsageSvpr |