Часто меня спрашивают студенты, что такое PGA? Это специальная область памяти в экземпляре Oracle. Итак привожу определение на английском языке.
The Program Global Area (PGA) contains information used for private or session-related information that individual users need. Again, this used to be allocated out of the shared pool. In Oracle 9i, a memory structure called the instance PGA held all private information as needed.
This alleviated the need for the shared pool to constantly resize its SQL area to meet the needs of individual sessions. Because the amount of users constantly varies, as do their private memory needs, the instance PGA was designed for this type of memory usage. The PGA contains the following:
✓ Session memory (сессионная память PGA Oracle)
• Login information
• Information such as settings specific to a session (for example, what format to use when dates are displayed)
✓ Private SQL area (выделенная область SQL)
• Variables that might be assigned values during SQL execution
• Work areas for processing specific SQL needs: sorting, hash-joins, bitmap operations
• Cursors
Надеюсь, все поняли данную заметку ;-)
