Displaying Cache Information 

You can display the hit rate of the caches in the Database Manager GUI. These hit rates show you whether the caches have been configured with enough space. The hit rates for the data cache and the converter are particularly important.

Prerequisites

The database instance is in the ONLINE operational state.

Procedure

...

       1.      Select the required database instance in the list of database instances.
Connect to the DBM server for this database instance if necessary.

       2.      Choose Instance ® Information ® Caches.

       3.      The following information is displayed for the different caches:

Accesses	Total number of accesses
Successful	Number of successful accesses
Unsuccessful	Number of unsuccessful accesses
Hit Rate (%)	Hit rate (number of hits as a percentage of the total number of accesses).

The current values of certain database parameters that can affect the caches are also displayed.

Result

The hit rate of the data cache should be at least 99% and the converter hit rate should be at least 98%.

Lower hit rates can occur for a short time, for example when tables are read for the first time, or when the table does not fit into 10% of the data cache in the case of repeated table scans. If the values are permanently lower than the recommended percentage, this is a sign of poor performance. In this case, the CACHE_SIZE general database parameter must be adjusted accordingly.