Zabbix Documentation 3.0

3.04.04.24.4 (current)| In development:5.0 (devel)| Unsupported:1.82.02.22.43.23.4Guidelines

User Tools

Site Tools


manual:config:items:history_and_trends

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
manual:config:items:history_and_trends [2015/10/27 13:38]
martins-v linking to item configuration
manual:config:items:history_and_trends [2018/10/12 07:24] (current)
martins-v minor grammar fix
Line 1: Line 1:
-==== - #3 History and trends ====+==== 3 History and trends ====
  
 === Overview === === Overview ===
Line 25: Line 25:
 While keeping shorter history, you will still be able to review older data in graphs, as graphs will use trend values for displaying older data. While keeping shorter history, you will still be able to review older data in graphs, as graphs will use trend values for displaying older data.
  
-<​note>​If history is set to '​0', ​Zabbix ​will only be able to calculate triggers that check the last valueHistorical values would not be stored in the database at all, except for the last value for the item itself.</​note>​+<​note ​important>If history is set to '​0', ​the item will update ​only inventoryNo trigger functions will be evaluated.</​note>​
  
 === Keeping trends === === Keeping trends ===
Line 38: Line 38:
 Trends usually can be kept for much longer than history. Any older data will be removed by the housekeeper. Trends usually can be kept for much longer than history. Any older data will be removed by the housekeeper.
  
-<​note>​If trends are set to '​0', ​Zabbix server ​does not calculate or store trends at all.</​note>​+Zabbix server ​accumulates trend data in runtime in the trend cache, as the data flows inServer flushes trends into the database (where frontend can find them) in these situations:​ 
 +  * a new hour has started and server receives a new value for the item; 
 +  * a new hour is about to end in less than 5 minutes (no new values) 
 +  * server stops
  
-<​note>​The trends are calculated and stored with the same data type as the original values. As the result the average value calculations of unsigned data type values are rounded and the less the value interval is the less precise the result will be. For example if item has values 0 and 1, the average value will be 0, not 0.5.+To see trends on a graph you need to wait at least to the beginning of the next hour (if item is updated frequently) and at most to the end of the next hour (if item is updated rarely), which is 2 hours maximum. 
 + 
 +When server flushes trend cache and there are already trends in the database for this hour (for example, server has been restarted mid-hour), server needs to use update statements instead of simple inserts. Therefore on a bigger installation if restart is needed it is desirable to stop server in the end of one hour and start in the beginning of the next hour to avoid trend data overlap. 
 + 
 +History tables do not participate in trend generation in any way. 
 + 
 +<note important>​If trends are set to '​0',​ Zabbix server does not calculate or store trends at all.</​note>​ 
 + 
 +<​note>​The trends are calculated and stored with the same data type as the original values. As result the average value calculations of unsigned data type values are rounded and the less the value interval is the less precise the result will be. For example if item has values 0 and 1, the average value will be 0, not 0.5.
  
 Also restarting server might result in the precision loss of unsigned data type average value calculations for the current hour.</​note>​ Also restarting server might result in the precision loss of unsigned data type average value calculations for the current hour.</​note>​