On Sun, 4 Jul 2010 19:13:11 +0300, Itschak Mugzach <[email protected]> wrote:
>Walt is correct on this. The serialization function should be implemented in >system code and currently it is not. I wonder if there is a third party >product that intercept the allocation/Open types and serialize on >directories and files. > There's little need. You're trying to imagine OS/360 problems in a UNIX environment, then perceive it as deficiency that UNIX doesn't supply solutions to problems it never had. >On Sun, Jul 4, 2010 at 4:54 PM, Walt Farrell wrote: > >> On the other hand, ENQ/DEQ is also advisory. The program accessing the >> resource needs to issue the appropriate ENQ and DEQ in order to maintain >> proper serialization. The question then becomes "what is the program?" >> >> For the case of the SYSDSN ENQ, the relevant program is in most cases >> Allocation, not the program that's going to use the data set, and the >> specific ENQ is based on the allocation DISP parameter. The SYSDSN ENQ is >> still advisory as far as Allocation is concerned, but out of the control of >> most data-accessing programs and thus mandatory from their perspective. >> I don't see it as "out of ... control". The programmer controls whether to request the allocation with DISP=SHR or DISP=OLD/MOD/NEW (unless you insist that is done in JCL and programmers don't write JCL because JCL is not a programming language). In both z/OS and UNIX, I can corrupt any data set to which I have update authority by overwriting it with garbage, or by updating it it with shared access. Unlike OS/360, the UNIX kernel has always protected directory integrity. OS/360 and its descendants make the advisory serialization more explicit than UNIX -- the OS default is exclusive access; the programmer must explicitly specify SHR. The UNIX default is shared. -- gil ---------------------------------------------------------------------- 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
