how to run fsck in solaris

A lot depends on what is causing the problem.  Since the disks are mirrored, if the file system has been made corrupt because of a software related issue (such as sudden loss of power), both disks will likely have the same problem.  Booting from the mirror won't help in this situation.

If the corruption is due to a malfunction in one disk, you need to replace the disk before trying to fix the filesystem or you will just end up doing it all again and again until the disk gives up and dies.

It would help to know how these disks are mirrored.  Are they set up as a RAID-1 in a hardware RAID controller and appear as a single disk in the OS?  Are they set up using Solaris Volume Manager as a mirror device wher ehte OS sees both disks but addresses them through a mirror device like /dev/md/dsk/d0?  Are they a ZFS mirror pool?  Are they a VxVM encapsulation?

Your choices and tasks will vary according to how the mirror is controlled.  Can you provide more information on that please?

Turnbuild

If the corruption is due to a malfunction in one disk, you need to replace the disk before trying to fix the filesystem or you will just end up doing it all again and again until the disk gives up and dies.

I think disk0 is corrupted due to malfunction. the other thing is  i didn't had any problem booting the system with disk1..

My question is now..
The procedure i described above. Is that possible. ?
Can i able to boot from disk1 (singleusermode) to fix fsck of disk0  fsck issue.

or
Do i need really need  to boot with cdrom in single usermode and fix disk0 fsck issue..

it depends on how the disks are mirrored.  Are you usinv a hardware raid lun, svm, zfs, vxvm, or something else to mirror the disks?

I am using SVM , no hardware raid configured..

Ok then, you'll need to break the mirrors to deal with the disks separately if you haven't already.  Change the BIOS to boot form the right half of the mirror (already done I believe) and reboot the server, use the metadetach command to remove the left mirror from the mirror device, then the metaclear command to destroy the concat/stripe device containing the left-mirror's slice.  Do this for each mirror defined on the disk.

Once that's done, you can do what you want with the disk.  If you want to mount the root slice and fsck it, feel free.  Bear in mind that, until you remirror the disk, you will not be protected from disk failures.  Also, when you re-mirror the disk, you'll overwrite any filesystem that is on it so it is probably a  waste of time trying to recover the file system on the detached disk.  

If the disk corrupted its filesystem due to a hardware problem, it will almost certainly be better to simply replace the disk and re-establish the mirrors using the new disk.  However, you can use the format utility to verify the disk forcing it to mark bad sectors bad and try again with the disk if you want.  I think it is likely you will find yourself doing this operation again and again until you have a good disk in the position however.

Tunbuild

I understand what you're trying to say But Unfortunately my question remains the same..
Let me change the scenario

Disk 3 (data disk  is showing data inconsistency)
what is the best only way to fix the issue..

A- boot the system with cdrom in single user mode and mount disk3 and run fsck..
B boot the system without cdrom in single usermode and mount disk3 and run fsck

To run fsck do I really need to have cdrom(os cd) or can I just run fsck by going in single user and mount disk 3 and run on it.

 cheers
Javeed A