Thanks for the post.

We ended up rebooting the machine, very, very annoying thing to have to do. But now sys mem is down to about 9Gb (in line with the DR machine) so definitely some kind of memory leak. Also the page scan rate is minimal (close to 0), i.e. what it should it be.

I don't know enough of how glance calculates 'system memory' so it is something I need to look into.

We've been through everything that has been recently installed and nothing appears to be the culprit. Saying that, we have noticed an issue with one application that uses dbms_pipes...and doesn't always close them. So that is something to consider, although the amount of memory a pipe uses is tiny.