Data Logging > Data Logging - Disk Space Requirements

The data is stored by SpecView in the Project Folder. This location is can be changed, but only with care, read User Guide: Changing Log Data location or folder.

NOTE: Log files are usually stored in the Project folder. To store the files in another location on the same computer, set the Path as described in User Guide: Changing Log Data location or folder. To backup the files to a network drive use a Logfile Conversion triggered by a Strategy Controller event, the Strategy Controller topic gives an example.

The amount of space taken up by log files depends on how often data is logged and how many variables have been selected for logging. Each numeric value logged to the files uses 14 bytes.

The SpecView logging system uses up to 7 files per day, all with the prefix YY_DDD

(Where YY is the year number, e.g. 03 for 2003, and DDD is the day within the year so 1st January is: 000 and the 1st February is: 031):

.LOG file - Variables data

.IDX file - Index file used in report conversion and Historical Replay

.LNM file - Names of the logged variables

.ALM file - Alarm data

.EVT file - Event data

.BTC file - BatchTag data

.CHN file - Chart Notes

Note: Not all of these files may be present for a given day, but all the files for that day MUST always be kept together as a set. These MUST also be kept in the same folder as their associated project files in order to be used.

The exact size of log files depends on the type of variables logged (for example, text strings take more space than integers). A typical variable logged every minute (which is the default rate) will take about 25KB of disk space per day. Therefore, 100 variables will take about 2.5MB per day.

Logged data should be Archived together with the Project.

Old logged data can be deleted using the button action: Logging: Purge Logfiles