On 4 July 2010 04:03, Edward Jaffe <edja...@phoenixsoftware.com> wrote:
> If IBM chooses to provide no equivalent function to SVC screening for PCs, > then proceeds to change numerous services to use PCs instead of SVCs, and > then complains because software that used to intercept SVC calls with SVC > screening now uses "unintended" programing interfaces to intercept the > equivalent PC calls, what can I really say about that? I just don't have > much sympathy... Two small points... SVC Screening was not something IBM implemented either to keep customers happy in general, or as a a counter to customers' often voiced need for continued source code availability. Rather, SVC Screening was implemented around 1980 in support of the short-lived IBM product VSPC (Virtual Storage Personal Computing), which, to some extent like CICS, attempted to run multiple users and their programs in a single address space. To keep one user from interfering with another, it was essential to be able to capture all or at least dangerous SVCs and treat them in a local manor. That customers and ISVs used this facility for all kinds of things almost as soon as it came along is hardly surprising. One could well argue that these uses were customers' and ISVs' own attempts to use a programming interface rather than the myriad non-standard schemes that had been in use from the beginning. In this light, IBM's failure to provide a general PC Screening interface has brought about the current situation. Peter Relson suggests, though doesn't exactly say, that screening of SVCs like ENQ is not a programming interface. But SVC Screening itself *is* a programming interface -- a very poorly documented one to be sure, but described in the mainstream manuals -- and the relevant TCB fields are clearly marked PI in the IKJTCB mapping macro and the control blocks book. Certainly not all SVC parameter lists are PIs, but some are documented as such, and it's a plausible argument that any generated by a published IBM macro such as ENQ are de facto a PI, since the MF=E and MF=L forms often require explicit and knowledgeable manipulation of them. Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
