Further to my earlier post, I delved into the pile of old manuals in the shed and found
VSAM Primer and reference, G320 5774, dated 1979!! Under Section 8.8, Single/Mass Insertion, I found the following: " .. Mass Insertion is a technique which is automatically used by VSAM when * Dataset is opened for output (ACB MACRF=OUT) * Sequential insertion technique is used (RPL OPTCD=SEQ) * The records to be inserted are sorted in ascending key sequence and * Are to be loaded into an empty dataset, or * Fit between 2 existing records, or * Are to be loaded at the end of a data set. ... Mass Insertion reserves defined FREESPACE and does not perform CI or CA splits (only 1 CI split is executed if records are to be inserted between existing records). This improves loading time. As there are no CI splits (except the first) this technique reduces DASD space usage dramatically. ... " It is also covered (although not to the same level of detail) in DFSMS "Using Data Sets". I checked z/OS 1.12 and it is in there, so I suspect it has not changed over the years. MKB ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
