What logs look like

Logs consist of primary and secondary files, and a control file. You define the number and size of log files and where they are stored in the file system.

A WebSphere® MQ log consists of two components:
  1. One or more files of log data.
  2. A log control file
A file of log data is also known as a log extent.

There are a number of log files that contain the data being recorded. You can define the number and size (as explained in Changing IBM WebSphere MQ and queue manager configuration information), or take the system default of three files.

In WebSphere MQ for Windows, each of the three files defaults to 1 MB. In WebSphere MQ for UNIX and Linux® systems, each of the three files defaults to 4 MB.

When you create a queue manager, the number of log files you define is the number of primary log files allocated. If you do not specify a number, the default value is used.

In WebSphere MQ for Windows, if you have not changed the log path, log files are created under the directory: 

C:\Program Files\IBM\WebSphere MQ\log\<QMgrName>
In WebSphere MQ for UNIX and Linux systems, if you have not changed the log path, log files are created under the directory: 

/var/mqm/log/<QMgrName>

WebSphere MQ starts with these primary log files, but if the primary log space is not sufficient, it allocates secondary log files. It does this dynamically and removes them when the demand for log space reduces. By default, up to two secondary log files can be allocated. You can change this default allocation, as described in Changing IBM WebSphere MQ and queue manager configuration information.