z/OS V1R6.0 DFSMS Access Method Services for Catalogs

ALLOCATEA Automatic record area bufferingR Record bufferingBFTEK(R) is not compatible with partitioned data sets extended (PDSE) andresults in an error if used with the DSNTYPE(LIBRARY) parameter.BLKSIZE(value)The data control block (DCB) block size for the data set. The maximumallowable decimal for the block size that is recorded in the DCB is 32,760. Youcan specify BLKSIZE for NEW or MOD data sets.For direct access storage device (DASD) data sets: If you do not use BLKSIZE, thesystem determines an optimal DCB block size for the new data set. To createthe DCB block size:vvvvThe system determines the block size if SMS is active and you do not assignthe block size.You can assign the block size through the BLKSIZE parameter.You can use the LIKE parameter to obtain the block size from an existingmodel data set.If you do not assign BLKSIZE or LIKE, the system can determine the blocksize from the BLOCK parameter.The block size that you assign for the DCB must be consistent with therequirements of the RECFM parameter. If you use:vvvvvRECFM(F), the block size must be equal to, or greater than, the logicalrecord length.RECFM(FB), the block size must be an integral multiple of the logical recordlength.RECFM(V), the block size must be equal to, or greater than, the largest blockin the data set. (For unblocked variable-length records, the size of the largestblock must allow space for the 4-byte block descriptor word, in addition tothe largest logical record length. The logical record length must allow spacefor a 4-byte record descriptor word.)RECFM(VB), the block size must be equal to, or greater than, the largestblock in the data set. For block variable-length records, the size of the largestblock must allow space for the 4-byte block descriptor word, in addition tothe sum of the logical record lengths that will go into the block. Each logicalrecord length must allow space for a 4-byte record descriptor word.Because the number of logical records can vary, estimate the optimum blocksize and the average number of records for each block, based on yourknowledge of the application that requires the I/O.RECFM(U) and BLKSIZE(80), one character is truncated from the line. Thatcharacter (the last byte) is reserved for an attribute character.For PDSEs:vThe system chooses the BLKSIZE if you do not explicitly specify it. IfBLKSIZE is given, the system treats the BLKSIZE as the length of thesimulated block. For create mode processing, the logical record length isequal to the block size if LRECL is not given. If you use LRECL, BLKSIZEmust conform to the LRECL and RECFM definitions. If you use:RECFM(F)RECFM(FB) or RECFM(FBS)BLKSIZE must equal LRECLBLKSIZE must be a multiple of LRECLChapter 4. ALLOCATE 35