Under some extreme data collection scenarios (that can be considered a suboptimal configuration), the history cache may be taken over by a few "spammy" items, disrupting DB history writes and slowing down the entire system. Once such values get into the history cache, it's difficult to do anything other than wait until the history cache becomes available.

To deal with such cases in the long term the data collection must be balanced with the resources available (DB performance, cache size, collection intervals, log item parameters, etc). However, to remedy such situations in the short term, Zabbix should also provide some tools. Specifically:

• Print history cache diaginfo once the history cache is full
• Clean up the cached values for the item once it's disabled (possibly, leaving the last one for logs to keep the state)
• Provide a runtime command to clean up the cached values by item id