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Author Topic: Please clear some doubts regarding Linux  (Read 1802 times)

Offline gauravbajaj

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Please clear some doubts regarding Linux
« on: August 20, 2008, 10:46:01 AM »
Hi All,
Need help here

I want to know regarding performance of oracle in Linux
Suppose oracle db is inastelled in a partition  like /dev/sda5

Oracle DBA's are cpomplaining that Oracle db is running very very slow, means its giving poor performnca somehow, Though it was running fine before

How to troubleshoot in above secenerio

I have given the iostat command but i need to know what we need to check wid below commands

iostat -x command

I belive that iowait should not been high for the disk, if suppose its giving high i/o wait , then what to ask to DBA Guys to make something which makes in less i/o wait

what all other paramaters we need to check in iostat command  and what should be ideal value of iowait so that we need not to worry?

Is vmstat is suitable in above scenerio?

I belive that in vmstat we need to check bi bo, si so paramaters, what should be the ideal value of these fields

Please let me know about your inputs to troubleshoot the situation like dis

My second question

Suppose a system is having 2GB of swap , I checked and found that its giving high memory blocks at buffer/cache+ in "free -m" command say about 1.5GB is there in buffer/cache +, what is meaning of that??

I belive that buffer/cache management is done by kernel itself and if a program is executing frequently and taking swap, so kernel keeps it in buffer /cache so that it dont .need to fatch it from Hard disk and access it much faster.

1 High Buffer/cache  in "free -m" command is good for system or bad?
2. Low Buffer/cache in "free -m" is good for system or bad?

Supose If i installed a new Linux OS, and i don't see much process running on the system but i would see that high buffer/cache+ in that? why is it so?

My 3rd Question

Suppose I installed the new kernel in Red Hat Linux and want to switch to that kernel without rebooting the system, Is it possible?? ( Its a physical system , no xen or VM env is there in it)

I have searched and found there is a utility called kexec available but  you need to install it , Is any other way is there to do that??

My 4th question

How to find its a Storage or local disk? I got the explanation by Dragon City but its unclear to me, as per him it depends upon the vendor, but i belive its not as we need not to know abt the vendor abt the same

DragonCity any more inputs here? I have a partition and I wana know wheather its a local or SAN.....

As per my last thread i mentioned the cat  /proc/scsi/scsi0 file and i talked abt dmesg | grep -i attach to know the same, but still it is not so much clear to me

My fifth question

Is there is any way to limit the memory to certain processes/users in linux

I belive that we can do from ulimit command, Can someone tell is it ok ? If yes  please let me know how to make it permanent? I belive we need to make entry in some file but i dont remember

 Could I have your valuable inputsfrom all  experts?

Thanks all

« Last Edit: August 20, 2008, 10:49:46 AM by gauravbajaj »