In the "Oracle9i Real Application Clusters Administration" manual, there is a chapter about sequence numbers generator. Before believing to the snake oil sellers, read the fine manual. Sequence numbers are guaranteed to be unique PER DATABASE. What they're not guaranteed is to come in ordered fashion. When sequence number are cached (that is the default), they're cached separately, for each instance. Each instance returns the contents of its cache, so it is possible for the smaller number being returned after a larger one. There is "ORDERED" flag to deal with that, but that can be extremely expensive and impose significant overhead on your cluster.
On 11/03/2003 10:39:26 AM, Hemant K Chitale wrote: > > > I have always been comfortable with the idea that Sequences continue to > guarantee > uniqueness even in OPS / RAC environments. > > However, a recent Builder.Com article by Scott Stephens on the SYS_GUID > function has these lines : > "Sequence generator numbers are guaranteed to be unique only for a single > instance, which is unsuitable for use as a primary key in parallel or > remote environments, where a sequence in each environment might generate > the same number and result in conflicts. An identifier created by SYS_GUID > is guaranteed to be unique for each database." > > Huh ?! Do the lines mean that a single sequence can have duplicate values > in the two instances of an RAC cluster ? > > > Hemant K Chitale > Oracle 9i Database Administrator Certified Professional > My personal web site is : http://hkchital.tripod.com > > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: Hemant K Chitale > INET: [EMAIL PROTECTED] > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > San Diego, California -- Mailing list and web hosting services > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > Mladen Gogala Oracle DBA Note: This message is for the named person's use only. It may contain confidential, proprietary or legally privileged information. No confidentiality or privilege is waived or lost by any mistransmission. If you receive this message in error, please immediately delete it and all copies of it from your system, destroy any hard copies of it and notify the sender. You must not, directly or indirectly, use, disclose, distribute, print, or copy any part of this message if you are not the intended recipient. Wang Trading LLC and any of its subsidiaries each reserve the right to monitor all e-mail communications through its networks. Any views expressed in this message are those of the individual sender, except where the message states otherwise and the sender is authorized to state them to be the views of any such entity. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Mladen Gogala INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
