Volume label

The DASD volume label is located in the third block of the first track of the device (cylinder 0, track 0, block 2). This block has a 4-byte key, and an 80-byte data area with the following content:

key

for disks with the compatible disk layout, contains the four EBCDIC characters VOL1 to identify the block as a volume label.

label identifier

is identical to the key field.

VOLSER

is a name that you can use to identify the DASD device. A volume serial number (VOLSER) can be one to six EBCDIC characters. If you want to use VOLSERs as identifiers for your DASD, be sure to assign unique VOLSERs.

You can assign VOLSERs from Linux® by using the dasdfmt or fdasd command. These commands enforce that VOLSERs:

• Are alphanumeric
• Are uppercase (by uppercase conversion)
• Contain no embedded blanks
• Contain no special characters other than $, #, @, and %
  Tip: Avoid special characters altogether.

Note: The VOLSER values SCRTCH, PRIVAT, MIGRAT, or Lnnnnn (An L followed by five digits) are reserved for special purposes by other mainframe operating systems and should not be used by Linux.

These rules are more restrictive than the VOLSERs that are allowed by the traditional mainframe operating systems. For compatibility, Linux tolerates existing VOLSERs with lowercase letters and special characters other than $, #, @, and %. Enclose VOLSERs with special characters in single quotation marks if you must specify it, for example, as a command parameter.

VTOC address

contains the address of a standard IBM® format 4 data set control block (DSCB). The format is: cylinder (2 bytes) track (2 bytes) block (1 byte).

All other fields of the volume label contain EBCDIC space characters (code 0x40).