Re: Does Oracle PGA take out memory out of SGA?

In a nutshell: No.

PGA is a different pool from SGA. And, more important, SGA has a static preallocated size. While PGA "size" is always a limit, and is allocated on demand.

Parameter pga_aggregate_target defines a somewhat *soft* limit for PGA. From 12c upwards the parameter pga_aggregate_limit (defaults to pga_aggregate_target*2) defines the hard limit.

In some setups using MTS some memory structures normally allocated from PGA are allocated from SGA. This is comprehensible as, in MTS, there isn't the 1:1 relation between session and process.

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*Att*

*Luis Santos*

Em qua., 31 de mar. de 2021 às 16:04, Amit Saroha <eramitsaroha_at_gmail.com> escreveu:

> Dear All,
>
> Please help me understanding PGA and SGA.
>
> I was under the impression that PGA and Memory and SGA Memory are
> differently allocated. But, in a recent situation, we observed *ORA-7445
> [kghalf] *and my DBA is saying - out of a total of 256 GB system memory
> one session's PGA consumed everything and only 8 MB was left for other
> sessions. But, apart from one process, no other processes were impacted so
> I have doubt that - Oracle consumes SGA memory and Allocates it to PGA of a
> single process.
>
> Please help me understand.
>
>
> Best Regards,
> Amit
>

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