Disabling file locking
If you use Network File System Version 3 (NFSv3) for storing transaction recovery logs, and you want to use automated peer recovery, you must first disable file locking.
Before you begin
- Modify the core group heartbeat settings to change the amount of time after which WebSphere® Application Server considers a server failed. For more information, see the topic about the high availability manager.
- Ensure that your network is safe from network partitioning by, for example, installing backup network adapters.
- Modify the workload management throttling so that the server cannot be overloaded.
About this task
WebSphere Application Server obtains an exclusive lock on the physical recovery log files whenever it is instructed to undertake recovery processing, and releases this lock when it is instructed to pass ownership of the logs to another server. Access to a recovery log is performed only when the exclusive lock is held.
NFSv3 supports exclusive file locks, but holds them on behalf of a failed host until that host can restart. In this context, the host is the physical machine running the application server that requests the lock and it is the restart of the host, not the application server, that eventually triggers the locks to release. See the topic about how to choose between automated and manual transaction peer recovery for more information.
To provide a more appropriate failover behavior, you can either use manual failover, and configure the system as described in Configuring manual peer recovery for the transaction service, or you can disable the use of exclusive file locking.
Procedure
- In the administrative console, click server_name > .
- Clear the Enable file locking check box.
- Click Apply or OK.
- Save your change to the master configuration.
- Repeat the previous steps for every server in the cluster.
- Restart the servers in the cluster for the changes to take effect.
Results
What to do next
Having taken steps to mitigate the risk to recovery log integrity when locking is disabled, you can tune the heartbeating parameters of the WebSphere Application Server high availability (HA) framework to change the conditions under which a server is considered failed. By considering the characteristics of applications, network, and peak workloads, determine an acceptable period of time after which the likelihood of an incorrectly diagnosed server failure is acceptably small.
A trade-off exists between reducing the risk of an incorrect diagnosis of server failure and increasing the time for automated failover and peer recovery to occur. By default, a server is considered failed after 20 heartbeats, with a 10-second frequency, are missed. These defaults are custom properties of the core group that you can modify.