RAM still in use after Compressor job finished

I was watching my RAM usage in Activity Monitor while compressing a QT (self contained) exported from FCP. It went up to over 10gb in use and then when Compressor was finished with the job the RAM usage never went back down again even after I quit out. With other programs my RAM usage goes down when I close them. I had to restart my system in order to free up the RAM again. Is this normal?

OS X 10.6.7
Compressor 3.5

Model Name: Mac Pro
Model Identifier: MacPro3,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 3 GHz
Number Of Processors: 2
Total Number Of Cores: 8
L2 Cache (per processor): 12 MB
Memory: 12 GB
Bus Speed: 1.6 GHz
NVIDIA GeForce 8800 GT - VRAM (Total): 512 MB

TIA for any help.

I think it's probably this issue:

Quote

Inactive: Memory stored from an application that is no longer running. OS X stores application data in a cache so that you can quickly relaunch applications a second time. If you start running out of free memory, the operating system will automatically start using inactive memory.

To clear inactive memory manually, go to Applications/Utilities/Terminal. When it launches, type purge and press enter. Note: it takes several seconds to process.

[www.digitalrebellion.com]

My software:
Pro Maintenance Tools - Tools to keep Final Cut Studio, Final Cut Pro X, Avid Media Composer and Adobe Premiere Pro running smoothly and fix problems when they arise
Pro Media Tools - Edit QuickTime chapters and metadata, detect gamma shifts, edit markers, watch renders and more
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Thank you very much. Since I saw it clear the amount of RAM used by other programs when they quit I thought it was specifically a Compressor issue. Maybe OS X was holding the RAM used by Compressor due to it being such a large amount. None of the other programs I checked used nearly as much RAM.

My next try was going to be finding out if I could clear it using OS X so thanks again!

After visiting your link I noticed that your post mentioned the "Inactive" memory. My "Active" memory stayed at 10gb. I'll do the same task later and verify that and see if it changes to "Inactive" after a bit.

Sidenote: I tried the "purge" command and got "command not found" but I can search for that myself as that's an OS X thing, just thought I'd mention it.