Setting up the history cache and database
PATROL provides two different ways of controlling how much parameter information, in the form of data points, that it stores in memory. The memory storage is referred to as the history cache. You can retain information in the history cache based on either how much information you want to store (number of data points), or how long you want to store information in memory.
These two storage methods are not mutually exclusive which is mentioned as follows:
- If you select to store history based on the number of data points, the agent writes all the data points for a parameter to the history database when that parameter collects the specified number of data points.
- If you select to store history based on a time interval, when the interval expires, the agent writes all data points for all parameters to the history database.
- If you activate both methods of storage, the agent writes information to the history database more frequently than if only one method is activated. The agent writes once when the time interval expires and once when a parameter collects the specified number of data points.
This history is not the same as events, which are kept in the event log repository file. PATROL Agent stops writing information to the history text file, param.hist, when the size of param.hist grows to 4 GB.