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Memmory [message #64954] Wed, 17 March 2004 12:21 Go to next message
Messages: 1
Registered: March 2004
Junior Member
i want to uderstand, how memmory is allocated. i.e where we create a session and run a query. what memmory structure are created and can we get the size to these memmory from v$ view.


Re: Memmory [message #64958 is a reply to message #64954] Thu, 18 March 2004 00:23 Go to previous messageGo to next message
Messages: 91
Registered: March 2004

When you connect to Oracle server, PGA is allocated. This contains tunable and untunable memory. To easily manage the PGA, use WORKARE_SIZE_POLICY=AUTO and PGA_AGGREGATE_TARGET=<max_amount_memory> that you would like to allocate for the server.

Once these parameters are set, you can use v$pgastat, v$workarea ....

Thanks ... IA
Re: Memmory [message #64971 is a reply to message #64954] Sun, 21 March 2004 04:06 Go to previous message
Messages: 1089
Registered: May 2002
Senior Member
there is shareable memory(SGA) and session specific memory(PGA) that come into play ,when user creates a session and performs queries/transactions. SGA(data buffer cache,shared pool(library cache,data dictionary cache),log_buffer(redolog buffer cache)) is preallocated and shared amongst all sessions.
Program Global area(PGA) is allocated per server process and is allocated outside of SGA.This consists of UGA(user global area) when using dedicated servers . In MTS(ie Shared servers), UGA resides in shared pool/large pool of SGA and is shared by multiple Shared server processes.

You can get information about these memory areas by querying V$sgastat,V$pgastat etc.

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