On Sun, 19 Feb 2012 18:11:13 -0600, Joel C. Ewing wrote: >> >Under Windows, a directory is closer functionally to the MVS/DOS concept >of a VTOC, as each volume has its own directory and you have to somehow >know which volume to consult -- although admittedly in a windows system >the number of volumes is typically very low. In Linux, if all volumes >are mounted, the directory plays a similar functional role to that of >the MVS catalog(s) and VTOCs combined. But in either case they are >obviously structurally different: finding an file entry in Windows or >Linux requires a progressive search through multiple directory levels >rather than just a single lookup of the full path name as with a data >set name in an MVS catalog. > There's some hint here that the single-level catalog lookup should have a performance advantage over a multi-level directory search. In practice, I find the opposite. Deleting several dozen catalogued data sets takes orders of magnitude longer than deleting a similar number of z/OS UNIX files. Admittedly, our lab configuration precludes a sysplex configuration that might otherwise greatly optimize catalog operations, I am told.
In practice, the z/OS search is not single-level; perhaps four: master catalog; user catalog; VTOC; PDS directory. And not mentioned here as yet is that the catalog can index offline volumes and automatically generate mount requests as needed. But this distinction seems to be vanisning. I have become accustomed on Solaris to receiving, infrequently, a message on my terminal that some file is temporarily unavailable; I must wait for it. I take this to mean that something analogous to HSM recall is in progress. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
