Tuesday, February 21, 2012

How to give a SAN stoarge in shared across the cluster using Fiber channel

In RAC environment storage should be in shared which means that all node in the cluster should be able to access the same storage array.

If we are using fiber channel method to connect from host to SAN storage. For each host there will be one unique WWN (World Wide Number) by giving this WWN to the LUN's which are mapped to the hosts in the cluster, then all the nodes in the cluster will be able to see those LUN's.

SCAN Listener

Single Client Access Name (SCAN) is a New Oracle RAC 11g R2 feature that provides a single name for clients to access Oracle Databases running in a cluster.

The benefit is that the client's connect information does not need to change if you add or remove nodes in the cluster. It provides Load balancing and Faliover for client connections to the database.

SCAN can be configured using either DNS (Domain Name Service) or GNS (Grid Naming Service).

SCAN IP address must be on the same subnet as that of our public network in the cluster.

It uses single name which resolves multiple IPs, we can check the scan configuration in DNS using nslookup

How ASM Disks are Mounting during Host Startup/Reboot while using ASMLIB

In Linux environment we are creating ASM disk uinsg Oracleasm utility which will be created after ASMLIB package has been installed. Here you might get a question on how this ASM disks are getting mounted during host startup/reboot. because in this method Linux admin will not add any entry for the new disk on neigher /etc/fstab not /etc/sysconfig/rawdevices.

The answer is, after we stamped a disk using ASMLIB, while starting up host, all the asm disks gets mounted while starting up the ASMLIB services.

Moreover while creating new disk using createdisk command itself it will assign appropripate user,group and its permission.