On Fri, 2002-07-12 at 18:36, Tony Pearson wrote: > > On z/OS, the ERASE ON SCRATCH option zeros-out the tracks containing data, > so that hardware compression can take advantage of this.
Actually, under z/OS there is a "deleted space reclaim" function that runs in background as part of the SVAA product (which used to be IXFP). It notifies the Iceberg/RVA/SVA to forget about specific tracks when it sees that datasets occupying those tracks have been logically deleted. There are two variants of this reclaim function: one runs periodically and scans VTOCs for tracks no longer allocated. The other dynamically frees tracks when datasets are deleted, via a hook into DADSM. So under z/OS, erase-on-scratch buys you pretty much nothing as far as disk space is concerned. I once asked the JES2 SHARE delegation if they implement erase-on-scratch for spool datasets for exactly this purpose, but they said no. -- David Andrews A. Duda and Sons, Inc. [EMAIL PROTECTED]
