Generating BS2000 labels (label generation)

VOLIN writes new labels on a volume either after the overwriting (statements FMT=YES or FMT=n) or immediately (statement FMT=NO).

If FMT=YES, the disk is overwritten once with a specific bit pattern, if FMT=n it is overwritten “n” times.

VOLIN concludes the initialization of the disk by transferring the new standard volume label. Its presence is a guarantee that the other labels on the volume have also been renewed.

How the disk is used following the VOLIN run depends on whether the initialization has created a private volume, a public volume or the Pubres disk of a pubset.

1. A private volume can be used by the BS2000 Data Management System immediately following the VOLIN run.

2. A public volume can be mounted during the subsequent loading of a BS2000 system (startup) or with a subsequent /IMPORT-PUBSET in order to extend an existing public volume set (pubset).

   The following attributes have global validity in the pubset and must be taken into account:

   • The VSN must match the pubset.

   • The PK (PAM key), AU (allocation unit) and TU (transfer unit) attributes must be the same as those of the Pubres. The following pubset types are thus possible:

     • K pubset (implicit AU=6 Kbytes)

     • NK2 pubset (implicit AU=6 Kbytes)

     • NK2 pubset with AU = 8 Kbytes

     • NK2 pubset with AU = 64 Kbytes

3. A volume which, according to the labels, has been generated by VOLIN for use as Pubres is inoperable and has no direct use in BS2000. An operational pubset can be directly created only with SIR or with an initial installation.

4. A disk initialized with VOLIN, no matter whether it is a private or public volume, can serve as the target volume in any physical data-saving operation (see the FDDRL backup program, and the Copy or Reload functions). Note, however, that the disk type, capacity, and block size of the target volume (2 Kbytes ) must be the same as that of the source volume.

Explanatory remarks on the various labels:

1. IPL block

   The IPL block is the first block (2 Kbytes) on the volume. VOLIN uses a dummy IPL here. If an attempt is made to load from this volume, the dummy IPL issues the message ILLEGAL LOAD FROM BS2000 DATA VOLUME vsn and causes the system to be placed in the wait state.

2. Standard volume label (SVL)

   The standard volume label is the second block (2 Kbytes) on the volume. It contains flags that identify the disk to the system as a particular volume, pointers to the other labels, and formatting information.

3. Format 5 label (F5)

   The start of this label is anchored in the standard volume label (SVL). The total number of blocks (2 or 4 Kbytes) allocated to this label depends on the type of disk. The format 5 label is used for managing the storage space on the volume. The smallest allocation quantity used by the BS2000 Data Management System is called an allocation unit (1 AU = 6 / 8 / 64 Kbytes, see description on "VOLIN Initialization of disk storage units", blocks are allocated consecutively, beginning with the first 2-Kbyte block). The most important part of the format 5 label is a table specifying which units on the volume are occupied and which are free. After a VOLIN run, all units preceding the F1 start address, as well as the units of the F1 label (see item 4 below), are marked as occupied.

4. Format 1 label (F1)

   This label begins at a unit boundary after the F5 label. Its start address is identical for all the disks of one type.

   The format 1 label exists only on private volumes. It contains the catalog of the files that begin on that volume. On public volumes, the F1 start address corresponds to the beginning of the storage space available for files. Together with the F5 label, the F1 label forms an area on the disk referred to as the VTOC area (VTOC = volume table of contents).

   System administration can define the length of the F1 label during the VOLIN run (by means of the F1SIZE statement; see "Description of the statements").
   VOLIN initializes the F1 label with empty catalog blocks.