Xref: alice comp.databases.oracle.server:60826 Path: alice!news-feed.fnsi.net!netnews.com!newsfeed.berkeley.edu!newsfeed.stanford.edu!paloalto-snf1.gtei.net!news.gtei.net!inet16.us.oracle.com!not-for-mail From: tkyte@us.oracle.com (Thomas Kyte) Newsgroups: comp.databases.oracle.server Subject: Re: newbe concurrency question Date: Sun, 08 Aug 1999 14:37:33 GMT Organization: Oracle Service Industries Lines: 49 Message-ID: <37b49614.8415741@newshost.us.oracle.com> References: <7o4rg3$6dq$1@news.xmission.com> Reply-To: tkyte@us.oracle.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: inet16.us.oracle.com 934122886 19009 130.35.30.103 (8 Aug 1999 14:34:46 GMT) X-Complaints-To: usenet@inet16.us.oracle.com NNTP-Posting-Date: 8 Aug 1999 14:34:46 GMT X-Newsreader: Forte Agent 1.5/32.451 A copy of this was sent to "Justin Call" (if that email address didn't require changing) On Mon, 2 Aug 1999 13:28:49 -0600, you wrote: >All- > >Lets say that I have several webservers running servlets using JDBC to >connect to an oracle database (8i for example). If I repeatedly execute the >following on all "clients": > >INSERT INTO SOMETABLE (SOMEINTCOLUMN) VALUES (SELECT FROM SOMETABLE >MAX(SOMEINTCOLUMN)); > >Do I ever duplicate values in SOMECOLUMN? absolutely you will. Unless you have a primary key (or unique) constraint on SOMEINTCOLUMN -- then everyone will wait in line and some people will succeed and some will perhaps fail. You might consider looking at sequences and instead: insert into sometable ( someintcolumn ) values ( your_sequence.nextval ); > If so, is the same true if the >database is replicated using parallel server? > OPS is not a replication implementation. Its a single copy of a database opened by many instances on different machines. it would see the same things as above. again, a sequence would be the best way to do this. >Any help would be much appreciated! > >-Justin > > > -- See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st Thomas Kyte tkyte@us.oracle.com Oracle Service Industries Reston, VA USA Opinions are mine and do not necessarily reflect those of Oracle Corporation