> Alex Brodsky was kind enough to point out to me that the ULUT has > to be serialized, and he referred me to the SETLOCK macro, which talks > about this. > > However, it seems to me that serialization is necessary only if you
> want to change something in the ULUT, and not if you just want to look > up real UCB addresses without having to be authorized. In other words, > my programs UCBDASD (CBT File 731), which just displays online DASD > UCB's, and the other program PACKRATU (CBT File 046), whose BACKENDU > module only has to find the UCB for the DASD unit that you want to > scratch datasets on, don't need a lock, because you're just DISPLAYING > the UCB's (UCBDASD) or finding their address initially (BACKENDU), and > not changing anything. So you don't need a lock, because you're not > changing anything, and therefore you don't have to get authorized in > order to obtain any lock. > > Alex himself pointed this out as well, but I wanted to bring it to > your attention, since some of you might want to write programs which > scan UCB's using this method. If you need to change something in the > ULUT itself, it needs to be serialized and the program has to be > APF-authorized to do that (I think). But if you're just doing lookups, > it doesn't seem to matter. > > Again, I want to point out that this is an "undocumented interface" > because it changes, and anyone who uses it, is obligated to keep track > of the changes. As long as you query the "type" field in the ULUT, > which is a one-byte field right after the "ULUT" eyecatcher, at ULUT+4, > and you account for the layout of that particular ULUT "type", it seems > that you're going to be OK. Keep in mind that programs which access data structures without the intended serialization may function incorrectly when the operating system changes the data structures. The ULUT, and UCBs, can be modified by the operating system when a new IODF is dynamically activated. Jim Mulder z/OS System Test IBM Corp. Poughkeepsie, NY ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
