FCB handling during OPEN processing

If a program uses the 24-bit interface, file processing is executed with a 24-bit TU FCB. In contrast to the 31-bit TU FCB (XS), space is reserved in the 24-bit TU FCB for the logical routines, which are actually copied into this space. Loading of the logical routines can be suppressed by means of the FORM=SHORT operand in the FCB macro. In this case, however, the user must handle all blocking and unblocking of records himself/herself. For normal processing of SAM and ISAM files, the file cannot be opened if FORM=SHORT is specified.