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RE: replication question

From: Kevin Lange <>
Date: Mon, 04 Mar 2002 11:43:27 -0800
Message-ID: <>

I have used both.  

Replication, like archive log movement , happens whenever you set it up to happen. That can be anywhere from every minute to once a day to beyond. It just depends on your needs. In the case of my old job, we had replication happening at different times for different tables. Our key table was replicating IMMEDIATELY upon any changes to the parent table. This happened via trigger. Other , not so important tables, would replicate at anywhere from 30 to 60
minutes. We did this using scheduled jobs.  

I see two real nice advantages of replicated databases. One, they are accessible. i.e. you can run reports, queries, etc on them. They are nothing more than instances that get updated via a foreign database. Two, depending on what kind of software you use, you can update the database from an outside source. We used to have data sent down from our DB2 database into our Oracle database using an oracle product called Replication Services
(nothing more than triggers and a specific data structure) and an IBM
product called Data Propogator.  

Archive log transport for standbys can happen in multiple ways also. The newer oracle versions support direct archiving from a production database to a standby database. I have not tried this yet but we are looking into it. Our current standby databases are brought up to date with a shell script that is scheduled via cron every 20 minutes.  

The thing about the standbys, they are all or nothing ... you can not just say I want only tables 1-10 to be updated. They all are. Also, in the older oracle versions, the standbys could not be accessed via software so you could not use them as any sort of read only database. This is not the case in a replicated database. But, they are also very easy to rebuild and resetup. Just copy your production files over, create a standby control file, and bring the databse up in standby mode. Very easy.  

Now... which would I recommend ??? Depends on your needs.  

If you really need to access that copy of the database for other purposes and you only want certain tables to be updated, then I would consider replication. If, on the other hand, you do not have to access the data
(until such a time as your production gets killed and you need your standby
up) and you need a fast way to rebuild the second database, I would suggest the Standby approach.  


-----Original Message-----
Sent: Monday, March 04, 2002 12:24 PM
To: Multiple recipients of list ORACLE-L

Is replication faster than a standby database. As I understand it, the standby database will be receive arch logs at preset intervals. Does replication have the same functionality and about how much data is sent to the replicated site.    

-----Original Message-----
Sent: Monday, March 04, 2002 10:44 AM
To: Multiple recipients of list ORACLE-L

The way I see it ..... the question comes down to whether or not you need two way replication or just one way. If both databases can update those tables and you need them synced between the databases then Advanced Replication would be the route. If all you need are data changes from 1 database to be replicated to another database then simple replication is all you need.

-----Original Message-----
Sent: Monday, March 04, 2002 6:43 AM
To: Multiple recipients of list ORACLE-L

Depends on your need.
You can have read only snapshots, updatable snapshots or multimaster...
Again if you think of multimaster... then you would need to make decision based on your application requirements about sync or async  

I donot have any expereince of snapshot replication. But, if you are planning multimaster replication, then better spend a couple of months studying it and testing on test boxes...  

Make 100% sure that your application really needs the replication and there is no other simpler option...  

Just 2 cents...  


Dear Gurus,
The clients will enter records to a database all day and I will update the other database .
I need to replicate 10 tables in a database to other database at a specific time.  

Do I need Advanced replication or basic replication . ? How can I understand that replication is supported in my both databases. ?  


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Author: Kevin Lange

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Received on Mon Mar 04 2002 - 13:43:27 CST

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