Program Global Area
A Program Global Area (PGA) is a memory region that contains data and control
information for a server process. It is nonshared memory created by Oracle Database
when a server process is started. Access to the PGA is exclusive to the server process.
There is one PGA for each server process. Background processes also allocate their
own PGAs. The total PGA memory allocated for all background and server processes
attached to an Oracle Database instance is referred to as the total instance PGA
memory, and the collection of all individual PGAs is referred to as the total instance
PGA, or just instance PGA.
The amount of PGA memory used and the contents of the PGA depend on whether
the instance is running in dedicated server or shared server mode.
The PGA is used to process SQL statements and to hold logon and other session
information. A large part of the PGA is dedicated to SQL work areas, which are
working memory areas for sorts and other SQL operations.
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