ClearSCADA organizes historical data into granules. Each granule is stored in its own file on disk. ClearSCADA can process and store several kinds of historic data. The granule content differs for each one:
Alarm Summary
Each granule contains the alarms associated with a block of items in a one hour period. The blocks of items are determined by the alarm summary stream size, (see Define the Stream size for Maximum Performance).
Configuration Changes
Each granule contains an audit of the changes made to a block of database items in a one hour period. The blocks of items are determined by the stream size, (see Define the Stream size for Maximum Performance ).
Event Journal
Each granule contains the events associated with a block of items in a one hour period. The blocks of items are determined by the journal stream size, (see Define the Stream size for Maximum Performance).
Historic Data
Each granule contains the historic data for one stream of one point / accumulator in a one week period. There are four streams of historic data called Raw, Modified, Annotation and Suppression, but only Raw and Suppression support overactive alerting.
If a granule becomes very large it can affect the performance and reliability of the system. The Historic Overactive feature provides a way of alerting you should an individual granule become too large, allowing you the opportunity to take action to prevent it becoming excessively large and having an adverse affect on the system. The feature also limits the maximum size of each granule. Once a granule reaches the maximum size all further records for the granule are discarded.
LOSS OF DATA
ClearSCADA allows you to raise alarms for Alarm Summary data, events and configuration change files that reach a configured limit. For information on how to specify the criteria for these alarms, see the topics that are listed in the gray footer section at the bottom of this topic. Select the relevant entry to display the topic that you require.