When CitectSCADA starts up for the first time, it creates the trend files necessary by each trend tag in the runtime system. (You can change this default using the [Trend}AllFiles parameter.)
A system of rotational history files is used to store the trend data. Data is stored in several files rather than in a single large file.
By default, there are 2 files (for each trend tag). You can change the default by specifying the number of files to use, for example:
Use ten files for the data, as in the diagram below.
The maximum number of files you can specify per trend tag is 270.
You can also specify the period between files, i.e., when a new history file is used, for example:
|1:00:00||Use a new file each hour|
|6:00:00||Use a new file every six hours|
|72:00:00||Use a new file every three days|
|Monday||Use a new file each week beginning on Monday|
|15th||Use a new file every month beginning on the 15th of each month|
|25th June||Use a new file every year beginning on the 25th of June|
You can also specify the time of day to synchronize the start of the history file; for example:
|6:00:00||Synchronize the file at 6:00 am|
|12:00:00||Synchronize the file at 12:00 midday|
|18:30:00||Synchronize the file at 6:30 pm|