Re: Oracle replication wasRe: Sybase 11 TPCC on DEC (your comments please)

In article <4e73f8$i93_at_news-e2a.gnn.com> GregC_at_megaweb.com (Norman M.(Greg) Carter Jr.) writes:
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>From: GregC_at_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
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>james.lawrence_at_epamail.epa.gov (Lawrence James) wrote:
 

>>In article <1f7cc$c2716.d4_at_news> Matthew Houseman <mhouseman_at_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 Received on Fri Jan 26 1996 - 00:00:00 CET