Continuous PGA increase in 11.2 & 12.1

We have 2 deployments, one running 11.2.0.4 and other running 12.1.0.2. In both databases, PGA is continuously increasing. We have identifying the sessions and the likely SP that is causing it.

Everybody says, check on the application side. Can somebody help to understand what do we need to check on the application side? We have confirmed that prepared statement is used. We are preparing the statement and thereafter we are doing bind and execute for every call to the SP.

• Can somebody help to understand what all are the causes of PGA increasing? Is this documented somewhere?
• Is there a scientific way to identify what is in the PGA? So that we can then check accordingly on the application side?