Pagefile

If you will reduce RAM amount you must go to Advance System setting, change paging file from system manage to Custom and put amount you want. After server restart you must come back and select System Managed Size again.

Windows will NOT automatically reduce your Page File size DOWN after amount of memory will be decreased.

Moving the system file onto a different partition will free up space on the system drive, but unless your pagefile is enormous it will only afford you some time to sort out the issue that is devouring the system drive space. I assume that you've already checked the temporary file folders and deleted their contents.
The other notorious hog of system disk space is the Windows update files folder, which can be cleaned up and/or moved to another partition; this is a more long-term solution to the problem.

There are numerous articles on the web that explain how to do this; the link I've posted is only one of a vast number:

https://blogs.technet.microsoft.com/sus/2008/05/19/wsus-how-to-change-the-location-where-wsus-stores-updates-locally/

Hope this helps.

Many thanks for your advice

My plan to decrease physical ram and move pagefile into different drive.

Shall I decrease the physical ram first and then pagefile or move pagefile first?

Or set the pagefile size manually, decrease the ram , move the pagefile.

After that set to system automatic

Many thanks Perarduaadastra

Mine is a file server and I'm decreasing physical ram to 16 to 12 GB. I have enough space on a second drive so moving onto that.

As you advice I'm going to leave it to system to handle the pagefile, not setting up manually.

Please advice is there anything else do I need to take care?

Thanks

👍