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# 11 Value cache

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#### Overview

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.

To enable the value cache functionality, an optional **ValueCacheSize**
parameter is supported by the Zabbix server
[configuration](/manual/appendix/config/zabbix_server) 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](/manual/config/items/itemtypes/internal).

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