Reclamation of Idle Compute Instances:
Idle Always Free compute instances may be reclaimed by Oracle. Oracle will deem virtual machine and bare metal compute instances as idle if, during a 7-day period, the following are true:
CPU utilization for the 95th percentile is less than 15%
Network utilization is less than 15%
Memory utilization is less than 15% (applies to A1 shapes only)
Don't allocate an insane amount of RAM and actually run applications on it? That's all I'm doing with mine. I have docker running with two applications. 1GB RAM allocated and 429MG used. Boom. Way above that 15% threshold.
I honestly think this is just about those people who overallocate resources then never actually do anything with it. Sure, Oracle can oversubscribe system resources but at some point you run into a wall because of the possibility that someone MIGHT actually use all the resources they've allocated. Until then they've got an expensive server not earning any money because everyone allocated 24GB of RAM just because they could.