Troubleshooting
Problem
Using IBM WebSphere Application Server V6.0 to create the transaction system for a bank, for example, WebSphere Application Server acts as the transaction manager and plays the key role at the system. The following detailed information about the log files used should be helpful for designing the transaction system. In WebSphere Application Server V6, we have 4 tranlog files(tranlog1, tranlog2, parterlog1, parterlog2), my questions are: 1. What is the different between tranlogs and parterlogs? 2. Does WebSphere Application Server use these 4 files at the same time? Or will WebSphere Application Server always use tranlog1/parterlog1, and use tranlog2/parterlog2 only when it can not use tranlog1/parterlog1 for some reason, such as a Disk I/O error and when the tranlog1/parterlog1 are both full? 3. From the high availability point of view, does WebSphere Application Server provide a dual write function or do we need to use RAID supported devices to store these files? And when we use RAID devices, is it necessary to store tranlog1/parterlog1 and tranlog2/parterlog2 separately at different disks?
Resolving The Problem
Answers:
1. A tranlog records details of transactions, specifically the transition of transaction states. partnerlogs record information about the resources involved in transactions, allowing the resources to be recreated when recovery takes place during a server restart.
2. WebSphere Application Server uses each pair of files independently of each other, so tranlog1 is not necessarily in use when partnerlog1 is. Each pair - for instance - tranlog1/tranlog2 are used in a flip-flop fashion: data is written to the active file until it fills up (data is never physically deleted from the files) when it copies the still active information to the secondary file, and starts to use that file as the active one. At this point the other file becomes inactive. A disk I/O error causes the transaction service to stop and the server to stop also.
3. WebSphere Application Server does not provide dual-write function, so the usual recommendation is to use some form of RAID supported disks to store the transaction and partnerlog files on. It is not necessary to store the files on separate disks. The two sets of files, tranlog1/2 and partnerlog1/2, however, are required to perform recovery.
If the tranlog files become corrupt, WebSphere Application Server is unlikely to detect the condition until a server restart is performed. The reason for this is that the files are not read during normal running - only in recovery are the tranlog files read. Corrupt logs do prevent the server from restarting.
Was this topic helpful?
Document Information
Modified date:
15 June 2018
UID
swg21211747