How to Use OS level monitoring utilities such as TOPAs , iostat , netstat and swap.
AS a DBA,it's very difficult to understand.
Please anyone provide step by step approach for that.When to start & Where to look.
Your question is understandable, but I'm afraid a forum is not a substitute for training or doing some research on your own. People have written books about Linux performance troubleshooting and there are numerous resources on the Web that should help you to get started. A good start might be the Performance Tuning guide. https://linux.oracle.com/documentation/
Maybe this is not exaclty an answer to your question, but, if you are +"more DBA than unix sysadmin"+ this could be realy usefull
Try to install and run the command atop
Is easiest to understand than iostat,top or topas and, like dba is more easy to find if the bottleneck is on I/O , memory or which device is being affected.
I hope it helps;-)
The atop utility is not part of the standard software distribution. However, it can be installed from the EPEL yum repository: http://fedoraproject.org/wiki/EPEL or install it directly, e.g.:
yum install http://dl.fedoraproject.org/pub/epel/6/x86_64/atop-1.26-3.el6.x86_64.rpm
As with any monitoring tool, it shows only statistics, but does not determine whether or not any system is configured properly or software configured to work efficiently. A system may allocate all available resources to a given task, which as such does not indicate a bottleneck.