Giovanni wrote: > > I've been using SMS for Dump datasets very succesfully but without using > some of the SMS features. I read about stripping, compress and extended > format but I've never read about multivol capability. Is there any sense > to think in multivol if we use stripping?. What would be the pros and cons > of each implementation?. >
Extended format data sets give you greater capacity in a number of ways. (a) The BLT reference values for extended format data sets are dense 3-byte values, so they can deal with roughly 16M blocks "per volume" where TTRs for conventional data sets use the final "R" byte very sparingly and give you more like 128K blocks per volume. As a consequence it is feasible for extended format data sets us use more than 64K tracks per volume effectively and still talk in terms of old 3-byte values to reference data set blocks. (b) Striping speeds sequential processing and exploits the increased capacity implied by BLT addressing so that tracks on several physical volumes can be viewed by the applications (SDUMP and IPCS in this case) as one logical volume. (c) Compression gets more data on a physical track. As both a system test and level 2 support site, we've seen an average saving of around 40% for the last several years when looking at substantial dump inventories. (d) Multi-volume for both traditional data sets and extended format data sets get you a new set of TTRs or BLTs respectively and, thus, lets you deal with very large dumps - at a cost of increased complexity for IPCS random dump access and reduced sequential recording and dump initialization speed. Sequential reading and writing take place to one logical volume at a time and don't exploit the entire set of volumes in parallel. I've heard 2nd-hand that DFHSM restrictions may influence your decision regarding use of striping and multi-volume data sets for your inventory, but that's not my area of expertise. Hopefully, some others who follow IBM-MAIN can supply some information on that front. Bob Wright - z/OS MVS Service Aids ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
