From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,3cd3b8571c28b75f X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-09-02 20:02:15 PST Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!arclight.uoregon.edu!wn13feed!wn11feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi_feed4!attbi.com!sccrnsc02.POSTED!not-for-mail Message-ID: <3F5559A4.8030507@attbi.com> From: "Robert I. Eachus" User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.2) Gecko/20021120 Netscape/7.01 X-Accept-Language: en-us, en MIME-Version: 1.0 Newsgroups: comp.lang.ada Subject: Re: A Customer's Request For Open Source Software References: <3F44BC65.4020203@noplace.com><20030822005323.2ff66948.david@realityrift.com> <3F4828D9.8050700@attbi.com> <3F4EA616.30607@attbi.com> <3F512BD1.8010402@attbi.com> <3F52AA5F.8080607@attbi.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 24.34.139.183 X-Complaints-To: abuse@comcast.net X-Trace: sccrnsc02 1062558133 24.34.139.183 (Wed, 03 Sep 2003 03:02:13 GMT) NNTP-Posting-Date: Wed, 03 Sep 2003 03:02:13 GMT Organization: Comcast Online Date: Wed, 03 Sep 2003 03:02:14 GMT Xref: archiver1.google.com comp.lang.ada:42088 Date: 2003-09-03T03:02:14+00:00 List-Id: Larry Kilgallen wrote: > In article <3F53B88E.7040405@attbi.com>, "Robert I. Eachus" writes: > > >>As I said, most RDBMSs already have the ability to bypass the OS and >>access disk drives directly. > > They do ? On what operating systems ? I guess we have a different idea of what bypassing the OS means. I was thinking of for example, Oracle on Solaris. You can go through the file system, bypass the file system and have Oracle manage a partition (raw mode), or give Oracle full control of the DISK device or devices. But even then you are right, the DBMS uses the standard device drivers. The difference is that if Oracle controls the entire disk, it can take control of the head positioning and other driver level functions. > I know compilers that read source that way, relying upon the OS paging > in the data as appropriate. But it is an individual performance/coding > tradeoff, not applied so universally as in Multics. Well, in Multics it is universal because there is no user level distinction between main memory and disk storage. It is all memory, and once you have linked to a segment, there are no further OS level commands to read and write it. Well, technically not. You could break the link to the segment if you wanted, or were running out of segment descriptors in your process. But breaking links was more likely to be a side effect of deleting the segment. A bit of magic here. If you were compiling a file that was part of an application the compiler would normally rename the old version of the code segment, not delete it. That way if someone else--or you in a different process--were executing the old code, the segment was still there. But you could then delete the old version to force users to use the new copy. What if the segment you were compiling was part of the operating system? Why should that be any different? So you could modify Multics on the fly. Occasionally with early versions of Multics, there were "flag days". There was an incompatable change to the OS, so at a particular point all the affected old segments were replaced with new versions. But they soon stopped. The reason that flag days happened was usually that someone had concluded that some data structure did not need an internal version number. Pretty soon it became accepted wisdom on Multics that every OS data structure needed a version number, including structures that contained structures with version numbers. -- Robert I. Eachus "As far as I'm concerned, war always means failure." -- Jacques Chirac, President of France "As far as France is concerned, you're right." -- Rush Limbaugh