System metrics monitoring

What’s in this document?

The database employs a number of metrics that help tune the memory parameters and performance. They can be found in the JMX console under the com.ontotext.metrics package. The global metrics that are shared between the repositories are under the top level package, and those specific to repositories - under com.ontotext.metrics.<repository-id>.


Page cache metrics

The global page cache provides metrics that help tune the amount of memory given for the page cache. It contains the following elements:




A timer for the pages that are evicted out of the page and the amount of time it takes for them to be flushed on the disc.


Number of hits in the cache. This can be viewed as the number of pages that do not need to be read from the disc but can be taken from the cache.


A timer for the pages that have to be read from the disc. The smaller the number of pages is, the better.


Number of cache misses. The smaller this number is, the better. If you see that the number of hits is smaller than the misses, then it is probably a good idea to increase the page cache memory.

Entity pool metrics

You can monitor the number of reads and writes in the entity pool of each repository with the following parameters:



a timer for the number of reads in the entity pool.


a timer for the number of writes in the entity pool.