describe the PGA,”Program Global Area (PGA) is a memory region that contains data and control information for each server process. An Oracle server process services a client’s requests. Each server process has its own private PGA that is allocated when the server process is started. Access to the PGA is exclusive to that server process
and the PGA is read and written only by the Oracle code acting on its behalf. The PGA is divided into two major areas: stack space and the user global area (UGA).”