BS2000 OS DX supports FBA disks in Pamkey or NK2 formatting. With Pamkey formatted disks, a block consists of 4 x 512 byte blocks (=data) + 512 bytes for the key (Pamkey), whereby the key consists of only 16 bytes. The waste caused by storing the key is therefore almost 20%. On top of that, the key has to be transmitted in a separate IO because it no longer fits in the FibreChannel frame. These disadvantages should be avoided by preferably using NK2 formatted disks and eliminating the 16-byte pamkey in the separate 512-byte block.
To eliminate pamkeys, PAMKEY files (files with the property BLKCTRL=PAMKEY) must be converted into files that either contain the system information contained in the key in the data block in a separate block control field (BLKCTRL=DATA) or no longer need this information at all (BLKCTRL= NO).
The block control field occupies the first 12 bytes of the data block and also contains the coded field identification used for checking for gaps. This block control field reduces the maximum usable record length of the data block.
Depending on the file access method defined in the ADD-FILE-LINK command, new file formats come into use as a result of PAM key elimination, which is detected by means of the BLOCK-CONTROL-INFO parameter. Further information on these new file formats can be found in manual [3] "Introductory Guide to Systems Support".
The following sections describe a number of special considerations for processing PAM files, which arise in the event of PAM key elimination.
SAM, ISAM and BTAM files are not affected by the elimination of the PAM key.