The Keep online for field in the ClearSCADA Server Configuration Tool's Historic settings allows you to specify the duration that Alarm Summary, Configuration Changes Auditing, Event Journal or Historic Data., is retained online. When this period of time expires, the historic data is deleted from the disk to allow space for the latest messages or data.
To configure the Keep online for duration:
- Access the ClearSCADA Server Configuration Tool.
- Expand the Historic Configuration branch.
- Select the historical data type you require, Alarm Summary, Configuration Changes Auditing, Event Journal or Historic Data.
- Enter the amount of time (in weeks) for the historic data to be retained in the Keep online fornweeks field.
- When you have defined the
Keep online for period:
- Proceed to the Archive after settings, (see Define the Archive Time for Historic Data).
Or:
- Apply the changes to the server.
- Proceed to the Archive after settings, (see Define the Archive Time for Historic Data).
Keep Online for - how it works (default settings)
This example illustrates how the Keep online for field affects the storage of Historic Raw data online. When a server is initially configured there is no data. In this example we assume that the Keep online for field in any of the data types is set to the default 52 weeks.
When the server starts and continues to receive data ClearSCADA creates historical data files (granules) to store the data online during the defined Keep online for period.
During the specified duration that the data is retained online, the data can change, for example, new event messages for that time period are reported or historic data can be modified (by ClearSCADA or manually).
When the archiving feature is enabled, there will be a set time at which the historic data can no longer be changed .
If you intend to archive historic data the duration period for which you retain data online needs to be greater than the period after which that data is archived. The duration period also determines whether you will be able to Creating a Replacement Archive Volume or Creating a Duplicate Archive Volume.
When the historic data exceeds the specified duration period, the data is automatically deleted from disk to allow space for the latest data.
So, if the duration is set to 52 weeks and starts on a Sunday midnight UTC (this only applies to Historic Raw Data), data that is stored historically on the first Sunday will be kept online for 52 weeks — the data from the first Sunday is deleted from memory at the beginning of the first Sunday of week 53. The data may be archived to media such as CD, DVD or hard drive during the 52 weeks, depending on the Archive AfternWeeks setting, (see Define the Archive Time for Historic Data).
Keep online for - Multi-server configuration
When you configure the server as part of a multi-server configuration the Keep online for period also defines the period that is synchronized between the servers, see Synchronization Process for Multi-Server Architectures.
When you configure the Keep online for period on a server as part of a multi-server configuration the Protect the Permanent Standby Servers when increasing online checkbox affects how space is allocated for historic data when you increase the value of the Keep online for period (see Protect the Permanent Standby Servers).
loss of data
The Index after setting can reduce the period that is synced between servers, see Manage the Size of the Primary Index. Data loss can still occur in certain scenarios for certain setting combination.
Keep online for - synchronizing with a Permanent Standby
This example illustrates how the Keep online for field can be configured in a multi-server system consisting of two Hot Standby server with a Permanent Standby server. In this example we assume that the Keep online for field in any of the data types has been set to 156 weeks for the Hot Standby servers. The Permanent Standby has been configured to store 520 weeks of data.
As Hot Standby servers are designed to provide redundancy to the database they should be configured identically, in this example they retain up to 156 weeks of data online. The Permanent Server is designed to provide backup and can be used to store historical data for a longer period of time.
When the historic data exceeds the specified duration period of the Hot Standby (MAIN) the data is automatically deleted from disk to allow space for the latest data.
The Permanent Standby server continues to store the historic data for 520 weeks. When the historic data exceeds the specified duration period of 520 weeks on the Permanent Standby, the data is also automatically deleted from disk to allow space for the latest data.
For more information about how this feature is affected by the other settings, 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.