Before a tape can be used by Kdat, it must be formatted by Kdat.
Some types of tapes must be formatted before they can be used to store data. This is not what Kdat does when formatting a tape. If your tape drive requires that the tapes be formatted before using them, then they must be formatted before they can be "formatted" by Kdat. Typically floppy tape drives require that their media be formatted, but DAT drives do not.
There are two ways to format a tape:
Select "Format Tape..." from the "File" menu.
Right click on the tape drive tree node, and select "Format Tape...".
You will be prompted for a name for the tape, and the stated capacity of the tape. Both of these parameters can be changed after the tape has been formatted. The tape name is only used to identify the tape to the user; it is not used to identify the tape index associated with the tape. Instead, a unique tape identifier is automatically generated and written to the tape. The stated capacity of the tape is used by Kdat to warn the user if there will not be enough space to complete a backup.
After entering the tape name and capacity, Kdat will proceed to format the tape. ALL DATA ON THE TAPE WILL BE LOST. Once Kdat has finished formatting the tape, the tape will be automatically mounted and is ready for use.