Using Trend History Files

Using CitectSCADA > Logging and Trending Data > Using Trend History Files

Using Trend History Files

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:

No. Files	Comment
10	Use ten files for the data, as in the diagram below.

When Citect begins logging, data is written to the first file.
At midnight the following Sunday, Citect writes to the second file.
At midnight the following Sunday, Citect writes to the third file, and so on.
After week 10, the first file is overwritten with new data.

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:

Period	Comment
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:

Time	Comment
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