Re: Oracle replication wasRe: Sybase 11 TPCC on DEC (your comments please)
In article <4e73f8$i93@news-e2a.gnn.com> GregC@megaweb.com (Norman M.(Greg) Carter Jr.) writes: >Path: nntp.teleport.com!news.reed.edu!sun.lclark.edu!netnews1.nwnet.net!news.u.washington.edu!news.alt.net!news1.alt.net!news.exodus.net!news.wni.com!noc.netcom.net!news4.noc.netcom.net!nntp.coast.net!howland.reston.ans.net!news-e1a.megaweb.com!usenet >From: GregC@megaweb.com (Norman M.(Greg) Carter Jr.) >Newsgroups: comp.databases.sybase,comp.databases.ingres,comp.databases.informix,comp.databases.oracle >Subject: Re: Oracle replication wasRe: Sybase 11 TPCC on DEC (your comments please) >Date: Thu, 25 Jan 1996 05:21:00 GMT >Organization: GNN >Lines: 47 >Message-ID: <4e73f8$i93@news-e2a.gnn.com> >References: <4cetgr$k87@news.infi.net> <4cj9ol$mcp@panix.com> <1f7cc$c2716.d4@news> <james.lawrence.142.00099AF3@epamail.epa.gov> >NNTP-Posting-Host: www-14-152.gnn.com >X-GNN-NewsServer-Posting-Date: 25 Jan 1996 05:12:07 GMT >X-Newsreader: Forte Free Agent 1.0.82 >Xref: nntp.teleport.com comp.databases.sybase:28845 comp.databases.ingres:18018 comp.databases.informix:27179 comp.databases.oracle:59268 >james.lawrence@epamail.epa.gov (Lawrence James) wrote: >>In article <1f7cc$c2716.d4@news> Matthew Houseman <mhouseman@arborsoft.com> writes: >>>isn't oracle replication simply PL/SQL? it may be easy to >>>use, but don't we all feel the need for speed for this sort >>>of technology? >>Yes it does use distributed transactions. Through the front door so to speak >>instead of through the back like sybase. Sybase should perform faster at the >>expense of a possible consistency problem. Oracle replicates the data and >>records that it has been successfully replicated as a single distributed >>commit. This ensures that it has been replicated. >I'm not sure what the implication is here - "front door", "back door". >The Sybase Replication System guarantees transaction delivery. Because >transactions are applied to replicate databases in a fashion >asynchronous to the primary database, there will be some latency >between the time an update is seen in the primary data and replicate >data. However, state consistency is achieved. That is, replicate >databases will be in the same state that the primary was at an earlier >point in time if not at the current point in time. >In comparing the Oracle strategy of a two-phased commit and Sybase's >strategy of asynchronous commits we find advantages and disadvantages >to both. Your particular implementation will probably dictate the best >for you. >While with the two-phased commit strategy you can be sure that all >replicate databases are consistent at any given time with the primary, >performance does suffer and the possibility of transaction rollback at >all sites increases with each replicate database entered into the >system - if one replicate database is unavailable, the transaction >fails at all sites. >With the asynchronous commit strategy, failure of one replicate >database does not affect the primary database or any other replicate >database. The transaction will be applied at the failing site once the >database is back on-line, while all the other databases in the system >committed the transaction as soon as it was received. >---------------------- >Greg Carter >Sybase InformationCONNECT Division >Replication Agent Development Actually, Oracle allows 2 phased commit and asynchronos replication. It depends upon what you want to do. Having a choice is a good thing. Sometimes one wants to require enterprise wide consistency (2 phase commit) and other times asynchronos replication will be most appropriate. Jim Kennedy