IBM 5280 Distributed Data System - Index of

ByteMeaningend The last byte in the parameter stnng must always be a biank (hex 40;unless a 14-character owner I D is specified.Note: This parameter string can also be used to open a data set on a securediskette; the OPEN instruction does not use the bytes before the fifth byte.The information that is taken from the data set lOB is as follows:ParameterDATA set name (NAME)Logical record length (RECL)Block size (BSIZ)Delete Character (DFLG)ExplanationThe data set name is mandatory for allocatinga diskette data set. It is optional for a printer.If this option .DATASET parameter isomitted, the length is set to equal to blocksize.Except for blocked and spanned data sets, theblock size must equal, or be a multiple of, thelogical record length. For blocked and spanneddata sets, BSIZ is an optional parameter; ifspecified it must equal sector size, and ifomitted the 5280 sets it to sector size.Delete flag; the character that is placed in theHD R 1 label during the allocate, and which willbe used to indicate a deleted record. Optionalfor I and E exchange; ignored for basic and Hexchange. Valid characters can be A-Z, 0-9, orone of the following symbols: . , - I % #@ : $ &.During the allocation operation, the data set organization byte of the HDR 1 label isset to blank (hex 40) for basic and H exchange data sets. It is set to D for I and Eexchange data sets. It is invalid to allocate a data set with the ALLOC instructionwhen the data set type is label update.Upon completion of the ALLOC operation, the allocated data set is also opened.The op code in the data set lOB is replaced with hex 00. Upon completion of theALLOC, or if an external status for insufficient physical buffer size (3430) or fortwo physical buffers specified with unequal sizes (3435) occurs, or if any group 7warning message is presented, the minimum number of 128-byte blocks requiredfor sufficient buffer size is placed into hex 78 of the data set lOB. If any otherexternal status occurs, this number is not placed into the lOB.The HD R 1 label is placed into the first 128 bytes of the physical buffer except forpointer 110 and SCS data sets that have the SW or ERS parameters specified in the.DATASET control statement.190