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Can we have multiple dataSources to single database [message #1694703]

Thu, 07 May 2015 09:25

Vijay Kumar

Messages: 6
Registered: May 2013

Junior Member

I am having spring webservice application with oracle as a database. Right now i have datasource created using weblogic server. Also using eclipse linkg JPA to do both read and write transactions(insert,Read and update). Now we want to separate dataSources for read(read) and wrtie(insert or update) transactions.

My current dataSource is as followed:
JNDI NAME : jdbc/POI_DS
URL : jdbc:oracle:thin:@localhost:1521:XE

using this i am doing both read and write transactions.

What if i do the following:
JNDI NAME : jdbc/POI_DS_READ
URL : jdbc:oracle:thin:@localhost:1521:XE

JNDI NAME : jdbc/POI_DS_WRITE
URL : jdbc:oracle:thin:@localhost:1521:XE

I knew that using XA datasource we can define multiple dataSources. Can i do same thing without XA dataSource. Does any one tried this kind of approch.

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Re: Can we have multiple dataSources to single database [message #1694859 is a reply to message #1694703]

Fri, 08 May 2015 14:12

Chris Delahunt

Messages: 1389
Registered: July 2009

Senior Member

I am not quite sure what you are after. Outside of XA, a transaction is tied to a particular resource. That resource needs to be used for reads and writes while in the transaction scope, or there are problems - when you insert/update/delete something, that change is only visible within that transaction resource. Reads on a different datasource/connection should not be able to see those changes until the transaction commits, which will break your persistence unit.

EclipseLink and JPA does have the ability to define transactional and non-transactional datasources, so that connections from the non-transactional datasource are to be used when outside a transaction. But while in a transaction (or joined to one), JPA is required to only use the defined transactional datasource and associated connection. EclipseLink makes exceptions and has the ability to define a sequence pool to obtain shared sequence values outside of a transaction, but I don't think this is what you are referring to.

If you want two different pools to be used depending on if you are doing a 'read' transaction vs a 'write' transaction, you should define two persistence units - one for each pool - and then have the application use the appropriate one for your read/write operation.

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