# Example 9: Customizing the Trace Log File

The commands in this example demonstrate different methods for customizing the event trace log file that Tracelog produces.

Circular file. The following command starts a trace log session with a circular log file. It uses the -cir parameter to specify a circular log file with a maximum size of 2 MB.

If you omit the maximum file size value (in this case, 2), Tracelog ignores the parameter and starts a session with a sequential trace log file.

``````tracelog -start MyTrace -guid MyProvider.guid -f testtrace.etl -cir 2
``````

Preallocated file. The following command starts a trace log session with a preallocated file. In this case, the file was preallocated to make sure that its large size could be accommodated before the trace session started.

This command uses the -seq parameter to specify a sequential event trace log file with a maximum file size of 128 MB and it uses the -prealloc parameter to request a preallocated file. Sequential files are the default, but the -seq parameter was used to specify a maximum file size, which is required for preallocated files. The -cir parameter can also be used to specify a maximum files size for -prealloc, if circular files are preferred.

``````tracelog -start MyTrace -guid MyProvider.guid -f testtrace.etl -seq 128 -prealloc
``````

Multiple files. The following command starts a trace log session that generates a series of smaller, sequential event trace log files, instead of one large file.

The command uses the -newfile parameter with a maximum file size value of 1 to start a new trace log file whenever the current log file reaches 1 MB. Also, the file name specified by the -f parameter includes the characters %d, as is required when using -newfile. The system substitutes a file counter value for %d when it creates each file.

``````tracelog -start MyTrace −guid MyProvider.guid -f testtrace%d.etl -newfile 1
``````

The resulting 1 MB files are numbered in the order that they are created, for example testtrace1.etl.