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swappiness
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Message Score Author Date
Hello gurus, we are switching our entire Oracle...... Matej Pagac Feb 25, 2020, 13:12
Matej, Your analysis makes sense. About 7 ye...... Score: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 Pts Philip Wisse Mar 05, 2020, 12:12

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Subject: swappiness
Author: Matej Pagac, Slovakia
Date: Feb 25, 2020, 13:12, 485 days ago
Os info: Red Hat Enterprise Linux Server release 7.6 (Maipo)
Oracle info: 19c
Message: Hello gurus,

we are switching our entire Oracle environment(RAC,DG,GG,...) from AIX to Linux and as a result I'm currently studying the oracle documentation for the Linux platform :)

Currently I'm in little doubt about setting the swappiness parameter.

I haven't found nothing specific in the "Database Installation Guide" or "Grid Infrastructure Installation and Upgrade Guide". There is only section explaining how to size the SWAP based on RAM.

What I found so far about the swappiness topic:

1)
RAC and Oracle Clusterware Best Practices and Starter Kit (Linux) (Doc ID 811306.1)

-> On kernel revision 2.6.18 and below set the kernel parameter vm.swappiness=100.
-> Stress testing has shown that vm.swappiness = 100 (default = 60) on kernel version 2.6.18 or lower can reduce or delay node evictions under conditions of heavy memory pressure due to large numbers of client connections or during login storms.

2)
https://access.redhat.com/documentation/en-us/reference_architectures/2017/pdf/deploying_oracle_rac_database_12c_release_2_on_red_hat_enterprise_linux_7/Reference_Architectures-2017-Deploying_Oracle_RAC_Database_12c_Release_2_on_Red_Hat_Enterprise_Linux_7-en-US.pdf

-> The recommendation of swappiness for Red Hat Enterprise Linux 6.4 or higher running Oracle databases is now a value between 1-20

3)
tuned-profiles-oracle-2.11.0-5.el7_7.1.noarch.rpm

-> sets the vm.swappiness = 10

4)
https://access.redhat.com/solutions/39188

-> Swapping for Oracle is not ideal and should be avoided as much as possible. The following tunable will tune the kernel to swap less aggressively.
-> vm.swappiness=10

My deduction is that 1 & 2 are already somehow old articles, therefore the swappiness = 10 should be used, and of course trying to avoid swapping =-]

Do you have experience with different value or another documentation from Oracle about this topic?

Thanks,
mTj
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Subject: Re: swappiness
Author: Philip Wisse, Netherlands
Date: Mar 05, 2020, 12:12, 476 days ago
Score:   Score: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 PtsScore: 100 Pts
Message: Matej,

Your analysis makes sense.

About 7 years ago I followed the advice of my sysadmin and used the value 100, those were different times.

Even 0 is a valid value: https://linuxhint.com/understanding_vm_swappiness/

Regards, Philip
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