Displaying Cache Statistics

Use

The cache statistics provide information about the number and data volume of accesses to the cache. You can see how often, and with what success, data objects are loaded from the cache. You can display global data (for all applications, regions, and activations of this instance), as well as local data (for the active session).

Prerequisites

Applications that use the VM Container must be running on the instance.

The cache must be active. See Caching in the VM Container.

Procedure

Display Statistics

On the initial screen of the VMC system administration (SM53) in the structure on the left side under Navigation choose Start of the navigation path Cache Info Next navigation step State End of the navigation path , and then in the top right-hand frame choose Hit Rate Statistics .

The top node on the screen that appears displays the global statistics across all applications, regions, and activations (at the top of the hierarchy).

The next level in the hierarchy contain the applications (in this example only veris), under these are the individual cache regions (folder icon ) with the activations (bar chart icon ). The numbers indicated for the regions and applications are the sums of the contents of the nodes (in the same subhierarchy), or as in the case of hits, the average number of hits from the subnodes.

Meaning of the Values

The statistics contain the following data:

Column	Meaning
Reads	Number of read accesses to the cache
Hits [%]	Cache hits as a percentage
Number of synchronous evictions	Number of objects evicted from the cache. This eviction is triggered while objects are being stored in the cache, and the cache has exceeded a specified size. While objects are being stored the system waits for the eviction to end.
Synchronous evictions (KB)	Size of the synchronously evicted objects from the cache (in kilobytes).
Number of asynchronous evictions	Asynchronous evictions of objects are executed periodically by autojava, once the fill level of the cache has exceeded a specified size.
Asynchronous evictions (KB)	Size of the asyncronously evicted objects from the cache (in kilobytes).

Local Measurement

Global statistics are continuously updated. Local statistics are kept in their active session and enable you to monitor the cache operations on the application server within a certain time period. You can, for instance record the statistics for a few calls to a process.

To collect and display statistical data for a specific actions, proceed as follows:

Choose to start at zero.

Note
This resets the local (session-specific) statistics. You can only display the cumulated (global) statistics; you cannot reset them. The statistics record the data during the whole life cycle of the VM Container.
Perform the required actions. You can update the statistical data by choosing (on the top tool bar).
View the results at the end of the recording.

Choose Reset Local Statistics to make a new recording or choose Display Cumulated Statistics , to switch to global (cumulated) statistics. In both cases the recording data is lost.