Problem: In a multi-server SharePoint farm, if you need to trace an issue, you have to log-in and review the ULS logs on each server in the farm. This process could be tedious in multi-server farms since you're not sure on which server the error has occurred.
Solution: Use the Merge-SPLogFile PowerShell cmdlet.
The Merge-SPLogFile cmdlet will consolidate the logs from all servers in the SharePoint farm into a single log file. You can run it from any server and it gathers data from the entire farm - to find issues.
Here is some examples of Merge-SPLogFile:
Merge-SPLogFile -Path D:\ErrorLog.txt -StartTime "20/10/2014" -overwrite Merge-SPLogFile -path "D:\ErrorLog.txt" -Correlation "Your-error-correlation-id"Here "path" refers to the log file name you want to create. If it already exists, use "Overwrite" switch. We can use parameters such as StartTime to specify the range of the log entries. There are other properties to help you narrow down the log search:
See the complete examples at Technet: Merge-SPLogFile Technet reference
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