You can configure transaction-related aspects of application servers to optimize the availability of those servers. This helps your transactions to complete or recover more quickly. After changing transaction-related properties of an application server, you must restart the server.
To configure transaction-related aspects of application servers for optimum availability, complete the following steps:
The performance of the disk also directly affects the transaction performance. In general, a global transaction makes two disk writes, one after the prepare phase when the outcome of the transaction is known (this information is forced to disk) and a further disk write at transaction completion. Therefore, the transaction logs should be placed on the fastest disks available.
In order for automatic failover of transaction log recovery to work in a WebSphere® Application Server cluster topology, network mounted devices must be used for the transaction logs, on a fast disk in a highly-available file system, such as a RAID device, that each cluster member can access.
You can configure hardware disk mirroring or dual-ported disks by using the administrative console to specify the appropriate file system directory for the transaction logs.
By default, an application server places transaction log files in a subdirectory of the installed WebSphere Application Server, where the subdirectory name is the same as the server name.
/IBM/WebSphere/AppServer/profiles/profile_name/tranlog/server1
/QIBM/UserData/WebSphere/AppServer/was_version/ND/profiles/profile_name/tranlog/server1
where was_version indicates the version number for this installation of IBM® WebSphere Application Server. For example V6 for WebSphere Application Server Version 6./IBM/WebSphere/was_version/AppServer/profiles/profile_name/tranlog/server1
where was_version indicates the version, release and modification number for this installation of IBM WebSphere Application Server. For example V6R0M2 for WebSphere Application Server Version 6.0.2.You can define a specific location for the transaction log directory for an application server by setting the Transaction Log Directory property for the server. If the directory for the transaction logs has not been created at application server start up, the directory structure is created for you.
If log files have been mirrored or can be recovered, these log files can be used when restarting a failed server, or they can be moved to another machine and another server can be started to undertake recovery, as described in the related tasks.
Never allow more than one application server to concurrently use the same set of log files, because each server will destroy the information recorded by the other, resulting in corrupt log files that are unusable for future recovery purposes.
On WebSphere Application Server, Network Deployment, the node agents automatically redirect these remote object references to the appropriate application servers on recovery. However, if the distributed transaction is between application servers that are not on WebSphere Application Server, Network Deployment, you must handle the redirection of remote object references so that transaction recovery can complete. For example, you must do this if an application server is deployed on WebSphere Application Server, Network Deployment edition) and runs distributed transactions with non-WebSphere EJB or Corba servers.
In particular, the default restart action of an application server not on Application Server WebSphere Application Server, Network Deployment is to use a different listening port address to the port when the server shuts down. This prevents transaction recovery from completing. To overcome this, you should always configure application servers to always use the same listening port address at each startup (see the ORB property com.ibm.CORBA.ListenerPort in the topic about Object Request Broker custom properties). You might have to make similar configuration changes to other application servers involved in transactions, to be able to access those servers during recovery.