The size of a tape determines the amount of data the Backup System can place on it. The tape size differs for different tape drives. In addition, the Backup System appends an end-of-file (EOF) mark after each fileset it dumps to tape. The size of the mark also affects the amount of space available for backup data on a tape. The values used for both of these figures are specified in the TapeConfig file once for each tape drive. Note that an EOF mark is appended after each fileset, not after each file.
If you do not know the tape capacity or EOF mark size for a tape drive, use the fms (file mark size) command to determine these values. The binary file for this command resides in the dceshared/bin directory. This command produces terminal output and an FMSLog file in the current directory; both the output and the FMSLog file list the tape capacity and the size of the EOF mark for the drive.
Note: Because this command inserts file marks onto the entire tape, it can take from several hours to more than a day to complete.
To determine the EOF mark size for a tape drive, do the following:
1. Make certain you have the w (write), x (execute), and i (insert) ACL permissions on the directory from which the command is issued. If the FMSLog file already exists in the directory, you need to have only the w permission on the file.
2. Insert a tape into the tape drive. The tape is overwritten while the command executes; you may want to use a blank tape or one that can be recycled.
3. Enter the fms command:
$ fms -device device_name
The -device device_name option specifies the name of the tape drive.
An example of this command and its terminal output follows; the command also writes similar information to the FMSLog file. In the example, the tape size for the drive named /dev/rmth1h is 2,136,604,672 bytes; the EOF mark size for the drive is 1,910,220 bytes.
$ fms /dev/rmth1h
wrote block: 130408
Finished data capacity test - rewinding
wrote 1109 blocks, 1109 file marks
Finished file mark test
Tape capacity is 2136604672 bytes
File marks are 1910220 bytes