Allowing db-is-shared to be true in a cluster with ReadOnly EJBs

Question

          Hi,
          We're running WL 6.1 SP2 on Solaris 2.8
          My question is about EJB caching in a cluster as we will shortly me moving to a clustered
          environment. The db-is-shared value for an EJB is normally meant to be always set
          to true in the case of a cluster because the database is shared across the cluster.
          However we are only using readonly Entity EJBs. We would expect to maintain the current
          db-is-shared value of false that we are using as our EJBs are very big and we cannot
          afford to go each time to the database. Will this be allowable in a cluster, that
          if you have readonly EJBs, you can maintain your db-is-shared value of false?
          Regs,
          Paul
          

Answer 1

          Cameron,
          We have a similar problem and would like to turn off db-shared property on entity
          beans. But this is what I got from BEA site. It says that we cannot do that in
          a clustered environment bcoz of caching limitations. We would like to use clustering
          ONLY for fail-over and would like not to hit the database so many time. Your thoughts
          please.
          Thanks
          Restrictions and Warnings for db-is-shared:
          Setting db-is-shared to "false" overrides WebLogic Server's default ejbLoad()
          container-managed-persistence behavior, regardless of whether the EJB's underlying
          data is updated by one WebLogic Server instance or multiple clients. If you incorrectly
          set db-is-shared to "false" and multiple clients (database clients, other WebLogic
          Server instances, and so forth) update the bean data, you run the risk of losing
          data integrity.
          Do not set db-is-shared to "false" if you set the entity bean's concurrency strategy
          to
          the "Database" option. If you do, WebLogic Server will ignore the db-is-shared
          setting.
          With database locking specified, the EJB container continues to cache instances
          of entity bean classes. However, the container does not cache the intermediate
          state of the EJB instance between transactions. Instead, WebLogic Server calls
          ejbLoad() for each instance at the beginning of a transaction to obtain the latest
          EJB data. This means that setting db-is-shared to "false" which prevents WebLogic
          Server from calling ejbload() at the beginning of each transaction is invalid.
          Also, due to caching limitations, you cannot set db-is-shared to "false" in a
          WebLogic Server cluster.
          "Cameron Purdy" <[email protected]> wrote:
          >db-is-shared implies that another client of the database can change
          >the
          >data, so yes, you can set it to false if the data is read-only.
          >
          >Peace,
          >
          >Cameron Purdy
          >Tangosol, Inc.
          >http://www.tangosol.com/coherence.jsp
          >Tangosol Coherence: Clustered Replicated Cache for Weblogic
          >
          >
          >"Paul Hammond" <[email protected]> wrote in message
          >news:[email protected]...
          >>
          >> Hi,
          >>
          >> We're running WL 6.1 SP2 on Solaris 2.8
          >>
          >> My question is about EJB caching in a cluster as we will shortly me
          >moving
          >to a clustered
          >> environment. The db-is-shared value for an EJB is normally meant to
          >be
          >always set
          >> to true in the case of a cluster because the database is shared across
          >the
          >cluster.
          >> However we are only using readonly Entity EJBs. We would expect to
          >maintain the current
          >> db-is-shared value of false that we are using as our EJBs are very
          >big and
          >we cannot
          >> afford to go each time to the database. Will this be allowable in a
          >cluster, that
          >> if you have readonly EJBs, you can maintain your db-is-shared value
          >of
          >false?
          >>
          >> Regs,
          >>
          >> Paul
          >>
          >>
          >
          >