Category Archives: Linux

Linux configurations for Oracle

Reconfigure OS Parameters After Linux Server Memory Upgrade

One of the Oracle database server ‘s memory is to be upgraded from 48GB to 72GB, so some parameters should be adjusted to take advantage of the newly added memory. 1)  Change ‘memlock’ parameter in /etc/security/limits.conf to 70G, which is … Continue reading

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How to Configure SHMMAX SHMMNI SHMALL ?

Every DBA is so familiar with those three kernel parameters in Linux — SHMMAX, SHMMNI and SHMALL. Most of the time, the default values are used by majority clients. But sometime, those three parameters need to be reconfigured to reflect the … Continue reading

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How to Disable SELinux or Set SELinux to Permissive Mode

It is suggested to disable SELinux or set SELinux to permissive mode for Oracle GI/RAC. Otherwise you might get similar below errors: Disk “ASM_DISK1” does not exist or is not instantiated Writing disk header: done Instantiating disk: oracleasm-instantiate-disk: Unable to … Continue reading

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High Swap Usage On Oracle Database Server

Situation: When investigating one client’s Oracle database server high swap memory usage, we find the swap space usage is constantly very high on this Linux server, which causes Oracle database a big performance issue. OS: RHEL 7.3 DB: Oracle 12.2.0.1 … Continue reading

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How To Flush DNS Cache

To flush DNS cache in Microsoft Windows : C:>ipconfig /flushdns To flush the DNS cache in Linux: # /etc/rc.d/init.d/nscd restart To flush the DNS cache in Mac OS X Leopard: $ lookupd -flushcache To flush the DNS cache in Mac … Continue reading

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How to Install rlwrap on Linux

rlwrap is an utility that allows you to use up and down arrows like in DOS environment. For Oracle commands like sqlplus, rman, adrci, we can do the same as in DOS environment to choose one of the history command … Continue reading

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Setting Shell Limits For Grid and Oracle Users

ulimit is to provide control over system resources. Setting limits to allow the user to use resources as much as really needed. so the system resources can be shared by all users fairly. To view current ulimit settings by typing … Continue reading

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