NNTP-Posting-Date: Sat, 07 Feb 2004 13:41:33 -0600 Reply-To: "Ron" From: "Ron" Newsgroups: comp.databases.oracle References: <548b9514.0402061242.64b4b0dd@posting.google.com> Subject: Re: Oracle Concepts Question Date: Sat, 7 Feb 2004 11:47:50 -0800 Organization: DBA Infopower X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: Lines: 49 NNTP-Posting-Host: 24.6.186.105 X-Trace: sv3-Uk6kKSlHL4idp4sZ4KL9CNN919uTBScnHF4b6AOypiZOXeieTTYv4NswG0SrwzJNac7j74Xr2+5fbfQ!quayJjaobBBhpFof9ACtmlkqU3kh4wYQWw17407IXUdrS440eUHdHR7xsKOQ X-Complaints-To: abuse@comcast.net X-DMCA-Complaints-To: dmca@comcast.net X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.1 "When a table has more than 255 columns, rows that have data after the 255th column are likely to be chained within the same block. This is called intra-block chaining. A chained row's pieces are chained together using the rowids of the pieces. With intra-block chaining, users receive all the data in the same block. If the row fits in the block, users do not see an effect in I/O performance, because no extra I/O operation is required to retrieve the rest of the row." Hope this answers the question. Regards, Ron DBA Infopower http://www.dbainfopower.com Standard disclaimer: http://www.dbainfopower.com/dbaip_advice_disclaimer.html "RK" wrote in message news:548b9514.0402061242.64b4b0dd@posting.google.com... > I was reading the Concepts manual and was puzzled by this sentence. > Can anyone elaborate on this: > > Tables are the basic unit of data storage in an Oracle > database. Database tables hold all user-accessible data. Each table > has columns and rows. Oracle stores each row of a database table > containing data for less than 256 columns as one or more row > pieces. > > What is this 256 column limit. I thought row chaining / migration > depended on row size. > > > See http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96524/c01_02intro.htm#20658 > > > Thanks > > rajXesh