Logger Tag Type Properties: Log Rate Tab
The Log Rate tab of the logger tag properties folder is used to identify the rate at which the data is recorded for the monitored tag. The log rate includes the interval at which data is to be monitored, the number of records that can exist in the data file, and the number of records that VTS will hold in memory before saving to the data file.
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The Interval field enables you to specify a period of time (in seconds or in fractions of a second) between logs of the value of the tag being monitored.
This property works with the Number of Records in RAM property to determine how often data is logged. It is recommended that you set your Interval (Seconds) and Number of Records in RAM properties to write to disk after a maximum time span of one minute. For example, setting the Interval (Seconds) field to 6 and the Number of Records in RAM field to 10 will write data to disk every 60 seconds. If the time span is set higher than one minute, there will be a lot of activity when VTS writes to disk, and you run the risk of substantial data loss in the event that the system should experience a failure.
The Number of Records in File field enables you to specify the number of records you wish to be written into the data file (*.DAT) where this logger tag stores the data for the basic I/O tag with which it is associated.
The Number of Records in File field is associated with the Maximum Possible Records and Create File Full Size checkboxes (see next).
The Maximum Possible Records checkbox identifies whether or not VTS should store the maximum possible records in the log file for this tag.
If the Maximum Possible Records checkbox is selected, the Number of Records in File field will be disabled, and VTS will store the maximum number of records in the log file for this tag. (The maximum number of possible records will be calculated by VTS, depending upon the number and size of the fields, but will never exceed 2^31.)
If the Maximum Possible Records checkbox is not selected, the Number of Records in File field will remain enabled, and you may enter a value between 100 and 100,000,000.
The Create File Full Size checkbox identifies whether or not VTS should create a full size data file for this logger.
If the Create File Full Size checkbox is selected, VTS will create the logger data file at the full size to prevent fragmentation of the data file as it grows larger (i.e. this option creates the file in a block on the disk, and allocates the file size to stop fragmentation).
If the Create File Full Size checkbox is not selected, the data file will grow as records are added, until the number of records reaches the maximum number of records in the file (as specified in the Number Of Records In File field). The oldest records will then be overwritten with the new records.
By default, the Create File Full Size checkbox is not selected; however, it is recommended that you do select it.
This field enables you to specify the number of records to buffer in RAM memory before writing the records to disk.
If the Number of Records in RAM field is set to 0, data is written to disk each time a new data sample is logged.
Setting the buffer to large numbers speeds the average data logging rate substantially, but requires RAM equal to the number of records specified. When the RAM buffer is full, the entire buffer is written to disk.
Note: The Number of Records in RAM property works with the Interval (Seconds) property to determine how often data is logged. It is recommended that you set your Interval (Seconds) and Number of Records in RAM properties to write to disk after a maximum time span of one minute. For example, setting the Interval to 6 and the Number of Records in RAM to 10 will write data to disk every 60 seconds. If the time span is set higher than one minute, there will be a lot of activity when VTS writes to disk, and you run the risk of substantial data loss in the event that the system should experience a failure.