Subpool durations

Question

11.0.2.0.2
When you use AMM, the shared pool is split into subpool durations.    The durations are "instance", "session", "cursor", and "execution".   I can find very little online related to the term "duration" as its meant in in its context here.  Does anyone have a note explaining further?
Reason for asking is I had a crash which was related to a  bug with this.  I have root cause, I know what the shared pool and subpools are.  Im just trying to understand the term "durations" here a little better.

Answer 1

thanks, yeah, that note has the basis of what affected my crash.  I had to set that _enable_shared_pool_durations  parameter as the workaround. 
The term is still not explained though.  I wont reproduce the full note here but in short it discusses the impact of setting _enable_shared_pool_durations and goes on to say
..... When set to FALSE, subpools within the SGA will no longer have 4 durations. Instead, each subpool will have only a single duration.
The advantage of this is that the performance issues documented in this note can be avoided. A duration will not encounter memory exhaustion while another duration has free memory......
I think its clear that while an SGA subpool is alive its known as a  "duration" but there doesnt seem to be any documentation around this.  How long does it live for? what determines the creation of a subpool duration?   .