# Log tag data

The HMI tag database does not store actual tag values. Instead, it defines which values are to be collected. The values themselves are stored in a value table on the HMI server. When the HMI server is turned off, the value table is cleared. To have a permanent record of tag values, log them to the data log file on disk.

To log tag values to disk, you create a data log model in the Data Log Model editor and specify the tags that are to be logged.

To see the current value of a tag (the value that is stored in the value table), design a graphic with display fields or a trend object to show you this information.

Tip: | The maximum number of tags that can be logged by the data log model is 10,000.

## See also

The Data Log Model editor

Value table