Afaik you can only set the Generate Logfile option in the document properties. And the log file will be saved in the same place as the .qvw file that generates it. If you want the logs elsewhere then you need to create a windows script that moves those log files to whereever you want them. And rename those logfiles too if you have several qlikview documents with the same name. And of course if you check a log file and see that something went wrong you'll have to figure out where the relevant .qvw is stored again, because it's now in a different place then the log file.
In other words: bad idea, don't bother.
As gwassenaar stated, you cannot set the Generate Logfile option at a server level.
What you can do though is set the User Preferences in Qlik Desktop to always use a logfile for new documenets, which is one of the first settings I change when installing the desktop.
I agree with the previous contributors about the setup and administration of log files.
Here are a couple of commands that we execute daily, in a batch file, to move the logs to a separate structure and maintain a months history there.
This command moves files that are over 24 hours old...
robocopy "C:\ProgramData\QlikTech\SourceDocuments" "C:\ProgramData\QlikTech\SourceDocumentsLogs" *.log /S /XX /NP /MOV /IS /MINAGE:1 /XD "*backup*" "*corrupt*"
This one deletes anything older than 31 days...
forfiles /p C:\ProgramData\QlikTech\SourceDocumentsLogs\ /s /m *.log /d -31 /c "cmd /c del @file| echo @FILE"
The only configuration needed is the establishment of a logs folder. In this case I have called it "SourceDocumentLogs".
Hope this helps,