Grid, GNS, SCAN

Oracle Grid Infrastructure
ASM and clusterware are installed into a single home directory called Oracle Grid Infrastruture

Interconnect NIC Guidelines

Failure to conrrectly configure the network interface cards and switches used for the interconnect results in sever performance degradation and possible node eviction.  Consider the following guidelines:

·         Configure the interconnect NIC on the fastest PCI bus

·         Ensure that NIC names and slots are identical on all nodes

·         Define flow control:  receive=on, transmit=off

·         For a better high available(HA) design would be a implement a redundant switch

strategy.

·         Define full bit rate supported by NIC

·         Define full duplext autonegotiate

·         Ensure compatible switch settings:

If 802.3ad is used on NIC, it must be used and supported on the switch
The Maximum Transmission Unit(MTU) should be the same between NIC and the switch

·         UPS socket buffer:  Default settings are adequate.  Increase the allocated buffer when MTU size has increased, netstat command reports errors, ifconfig command reports dropped packets or overfolow

·         Jumbo frames are not an IEE standard and need to test carefully

Clusterware Startup

·         Oracle Clusterware is started by the OS init daemon

h1:35:respawn:/etc/init.d/init.ohasd run >/dev/null 2>&1 </dev/null

·         Oracle clusterware installation modifies the /etc/inittab file to restart ohasd in case of a crash

GNS – Grid Naming Service
GNS assumes that there is a DHCP server running on the public network with enough addresses to assign to the VIPs and single client access name (SCAN) vips.  With GNS, only one statistic IP address is required for the cluster, the GNS VIPs.  

cat /etc/named.conf
cluster01.example.com # cluster sub-doman# NS cluster01-gns.example.com
cluster01-gns.example.com 192.0.3.154 # cluster GNS address

A request to resolve cluster01-gns.example.com would be forwarded to GNS on 192.0.3.154
Each node in the cluster runs a multicast DNS (Mdns) process.

SCAN – Single Client Access Name
The single client access name (SCAN) is the address used by clients connecting to the cluetr
The SCAN is a domain name registered to three IP addresses, either in the DNS or the GNS
The SCAN provides a stable, highly available name for clients to use, independent of the nodes that make up the cluster.