A NK4 ISAM file has the following file attributes:
BUFFER-LENGTH=*STD(SIZE=n) where n is an even number
BLOCK-CONTROL-INFO=*WITHIN-DATA-4K-BLOCK
Both file attributes can be specified by means of the ADD-FILE-LINK command or FILE macro.
A NK4 ISAM file is created under the following conditions:
Pubset: 4K
BUFFER-LENGTH: not specified /
*STD(SIZE=n)
where n is an even number
BLOCK-CONTROL-INFO: not specified /
*WITHIN-DATA-BLOCK /
*WITHIN-DATA-4K-BLOCK
If FILE-ATTRIBUTES=*INPUT-FILE is specified in the ASSIGN-OUTPUT-FILE statement, the block size and BLOCK-CONTROL-INFO attributes of the input file are transferred to the output.
If the input file is an ISAM file and specifies BLOCK-CONTROL-INFO=*WITHIN-DATA-2K-BLOCK, it is entered with BLOCK-CONTROL-INFO=*WITHIN-DATA-BLOCK. This means that the file can be set up with WITHIN-DATA-2K-BLOCK or WITHIN-DATA-4K-BLOCK, depending on the pubset on which it is created.