Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!cs.utexas.edu!uunet!mcvax!ukc!icdoc!bilpin!nick From: nick@bilpin.UUCP (Nick Price) Newsgroups: comp.databases Subject: Re: Use of Sys V IPC features by RTI Ingres Summary: Lock Managers etc Message-ID: <1599@bilpin.UUCP> Date: 4 Jul 89 09:37:17 GMT References: <386@odi.ODI.COM> Organization: SRL, London, England Lines: 42 In article <386@odi.ODI.COM>, dlw@odi.com (Dan Weinreb) writes: > A few weeks ago, I believe someone mentioned that the new version of > RTI's Ingres makes use of one of the System V IPC features (shared > memory segment or semaphores; I'm not sure which, but it doesn't etc etc > Dan Weinreb Object Design, Inc. dlw@odi.com Most (ALL?) DBMS systems under Unix require IPC of some sort. Ingres requires shared memory and semaphores for the shared memory lock manager which seems to be the favoured lock manager for most Ingres/Unix systems. Prior to this lock manager being available RTI shipped a lock daemon (still do) which was fairy slow but easily installable and a lock driver (kernel pseudo device driver). The driver obviously required linking in the kernel and was sometimes a problem to install. DBMS vendors are not always the best people to document a kernel build on a forein box! These days Unix manufacturers generally ship configurable kernels and a bullet proof interface to re-link and reboot, so installing IPC should not be a problem, however their default supplied values are not always sufficient. ORACLE for example is generally happier if it can place it's SGA (a large shared memory area) in a single segment, or can attatch two or more segments contiguously. This generally requires a few tries to get it right. Moreover I wonder how many installations are running poorly because IPC parameters are not set up optimally for the DBMS? I have certainly seen quite a few over the last few years. In summary - *don't* complain if the Unix vendor doesn't ship IPC configured in your default kernel. If you don't need it then you won't notice that it's missing and you are saving physical memory which costs money. *Don't* complain if DBMS vendors utilise IPC. DBMS's are complex system products, and as such you should expect to spend some considerable time getting things installed and running *well*. *Do* complain if the Unix supplier doesn't ship a reconfigurable kernel or an interface to rebuild it. If they don't look for another box to run your DBMS. :^) -- _______________________________________________________________________________ Nick Price SRL Data || Apple link : UK0001 1 Perren Street London NW5 3ED || UUCP : nick@bilpin.uucp Phone: +44 1 485 6665 || Path : mcvax!ukc!icdoc!bilpin!nick