SGA size vs SWAP space in Oracle RAC

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Question :

I’ve searched and read wide about the good practices of configuring swap space for Oracle Database installation. I am aware that for 1-2GB RAM, swap has to be 1.5x. For between 2GB and 8GB, swap needs to be equal to SGA. Above 8GB, swap will be twice SGA size (I stand to be corrected).

However, just yesterday, someone introduced something that got me confused. He said, “For Oracle Database or Oracle RAC on systems, available swap space must be at least equal to the sum of the SGA sizes of all instances running on the servers.”

I am a bit confused because I am aware that even though it is a RAC environment, each server has its OS and maintains its internal memory separately hence, the swap for each serverdoesn’t have to be equal to the sum of SGAs as indicated by my colleague.

Can anyone please help me understand what the correct value should be?

Answer :

Typically:

Server Configuration Checklist for Oracle Database Installation

Swap space allocation relative to RAM (Oracle Database)

Between 1 GB and 2 GB: 1.5 times the size of the RAM
Between 2 GB and 16 GB: Equal to the size of the RAM
More than 16 GB: 16 GB

Then there is Solaris…

Server Memory Minimum Requirements

Note:

On Oracle Solaris, if you use non-swappable memory, like ISM,
then deduct the memory allocated to this space from the available RAM
before calculating the swap space. If you plan to install Oracle
Database on systems using DISM, then available swap space must be at
least equal to the sum of the SGA sizes of all instances running on
the servers.

It is about summing the SGAs of multiple database instances on the same server, not about multiple database instances in a cluster on different servers (RAC).

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