Edward Jaffe wrote: | But would that not require "active" data movement/cleanup | whenever a block is freed?
and of course it would. How much of this would be required appears to depend upon what kind of member-replacement process is going on. There is some evidence---my sample is from six shops but for only 113 PDSEs---that an 80-20-like process is frequent, i.e., that 80 percent of the replacement activity is with only 20 per cent of the members. If this is common then keeping a list with counts of the last n replacement operations weighted for duplications would make it possible to use a very small amount of this sort of thing to great advantage. Shane's point merits comment too. PDSEs were radically under-instrumented at the beginning and still are; for this reason discussion of their deficiencies quickly degenerates into competitive anecdotage. One of the largest contributions IBM could make just now would be to greatly improve optional SMF-based instrumentation for PDSEs, We all understood the deficiencies of PDSs, and PDSEs were a laudable initiative, but they were also a half-hearted or, perhaps better, underbudgeted one. John Gilmore, Ashland, MA 01721 - USA ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
