Historian and Data Logging > Configuring Historian Tables
  
Configuring Historian Tables
By default, the tag historian database has one table configured. The table settings control when tag values are written to the historian and how long the values stay in the historian. If you want some tags to have different settings, you should configure additional tables with the settings you need and assign tags to the appropriate table.
The table configuration is independent of the Database selected to store the information, as described in Historian Database Provider.
If you want some tags to have different settings, such as the logging interval, you should configure additional tables with the settings you need and assign tags to the appropriate table. You can also edit the settings of the default table.
In general, do not store more data than you need. Storing a large amount of data slows the recovery of that data. You should use triggers and deadbands that are as large as possible, to ensure you have the information you need, without overloading the system.
To configure a historian table:
1. Go to Edit > Tags > Historian.
2. Do one of the following:
•To edit an existing table, select it from the Historian Tables drop-down list and click Config.
•To create a new table click New.
3. Enter or select information, as needed.
 
Option
Description
Database
Display-only name of the current tag historian database.
Table Name
Enter a name for table in the database.
Auto Create
Select to have the system automatically create the table in the database.
Save on Change
Select to store data in the table (add a row) every time a tag associated with the table changes.
Trigger
Use to store data in the table every time a tag or tag property changes. When used with the Save on Change option, the system stores data in the table when either the tag value changes or the Trigger value changes.
Time Deadband (Log TimeSpan)
Enter the minimum logging interval, that is, how long the system must wait after storing the value of a tag before storing a new value. Use with the Save on Change option to avoid creating too many records in the database.
Life Time
Number of days to retain the historian data. After that time, the older rows are automatically deleted from the database. To never delete data, leave this field blank or enter 0 (zero).
Compress
Number of the days before compressing the data. The compressed data is still available to trend charts and scripts, but access is slower. To never compress the data, leave this field blank or enter 0 (zero).