To make the calculation of trigger expressions, calculated items and some macros much faster, a value cache option is supported by the Zabbix server.
This in-memory cache can be used for accessing historical data, instead of making direct SQL calls to the database. If historical values are not present in the cache, the missing values are requested from the database and the cache updated accordingly.
Item values remain in value cache either until:
Value cache status can be observed by using the server runtime control option
diaginfo=valuecache) and inspecting the section for value cache diagnostic information. This can be useful for determining misconfigured triggers or calculated items.
To enable the value cache functionality, an optional ValueCacheSize parameter is supported by the Zabbix server configuration file.
Two internal items are supported for monitoring the value cache: zabbix[vcache,buffer,<mode>] and zabbix[vcache,cache,<parameter>]. See more details with internal items.