In a RAC environment the buffer cache is global across all instances in the cluster and hence the processing
differs.The most common wait events related to this are gc cr request and gc buffer busy

GC CR request: the time it takes to retrieve the data from the remote cache

Reason: RAC Traffic Using Slow Connection or Inefficient queries (poorly tuned queries will increase the amount of data blocks
requested by an Oracle session. The more blocks requested typically means the more often a block will need to be read from a remote instance via the interconnect.)

GC BUFFER BUSY: It is the time the remote instance locally spends accessing the requested data block.

srvctl start instance -d db_name -i “inst_name_list” [-o start_options]
srvctl stop instance -d name -i “inst_name_list” [-o stop_options]
srvctl stop instance -d orcl -i “orcl3,orcl4″ -o immediate
srvctl start database -d name [-o start_options]
srvctl stop database -d name [-o stop_options]
srvctl start database -d orcl -o mount

OIFCFG – allocating and deallocating network interfaces
OCRCONFIG – Command-line tool for managing Oracle Cluster Registry
OCRDUMP – Identify the interconnect being used
CVU – Cluster verification utility to get status of CRS resources

Oracle clusterware manages CRS resources based on the configuration information of CRS resources stored in OCR(Oracle Cluster Registry).

Fast application Notification as it abbreviates to FAN relates to the events related to instances,services and nodes.This is a notification mechanism that Oracle RAc uses to notify other processes about the configuration and service level information that includes service status changes such as,UP or DOWN events.Applications can respond to FAN events and take immediate action.

FAN UP and DOWN events:

FAN UP and FAN DOWN events can be applied to instances,services and nodes.

Use of FAN events in case of a cluster configuration change:

During times of cluster configuration changes,Oracle RAC high availability framework publishes a FAN event immediately when a state change occurs in the cluster.So applications can receive FAN events and react immediately.This prevents applications from polling database and detecting a problem after such a state change.

Oracle RAC is composed of two or more instances. When a block of data is read from datafile by an instance within the cluster and another instance is in need of the same block,it is easy to get the block image from the insatnce which has the block in its SGA rather than reading from the disk. To enable inter instance communication Oracle RAC makes use of interconnects. The Global Enqueue Service(GES) monitors and Instance enqueue process manages the cahce fusion.

GRD stands for Global Resource Directory. The GES and GCS maintains records of the statuses of each datafile and each cahed block using global resource directory.This process is referred to as cache fusion and helps in data integrity.

Oracle RAC is composed of two or more database instances. They are composed of Memory structures and background processes same as the single instance database.Oracle RAC instances use two processes GES(Global Enqueue Service), GCS(Global Cache Service) that enable cache fusion.Oracle RAC instances are composed of following background processes:
ACMS—Atomic Controlfile to Memory Service (ACMS)
GTX0-j—Global Transaction Process
LMON—Global Enqueue Service Monitor
LMD—Global Enqueue Service Daemon
LMS—Global Cache Service Process
LCK0—Instance Enqueue Process
RMSn—Oracle RAC Management Processes (RMSn)
RSMN—Remote Slave Monitor

RAC stands for Real Application cluster. It is a clustering solution from Oracle Corporation that ensures high availability of databases by providing instance failover, media failover features.

Assuming that the cluster is up and running and also assuming that you can connect successfully to one of the nodes.

Add redo groups to node2
alter database add logfile thread 2 ‘/u02/oradata/myrac2/redo04.log’ size 10m;
alter database add logfile thread 2 ‘/u02/oradata/myrac2/redo05.log’ size 10m;
alter database add logfile thread 2 ‘/u02/oradata/myrac2/redo06.log’ size 10m;
alter database enable thread 2;

Create undo tablespace for the second node:-
create undo tablespace UNDOTBS2
datafile ‘/u02/oradata/myrac2/undotbs201.dbf’ size 40m;

Set instance specific parameters in the spfile
alter system set cluster_database_instances=2 scope=spfile;
alter system set undo_tablespace=UNDOTBS2 scope=spfile sid=’myrac2′;
alter system set instance_name=myrac2 scope=spfile sid=’myrac2′;
alter system set instance_number=2 scope=spfile sid=’myrac2′;
alter system set thread=2 scope=spfile sid=’myrac2′;
alter system reset local_listener scope=spfile sid=’listeners_rac2′;
alter system reset remote_listener scope=spfile sid=’*';

Now ensure that both instances init.ora files point to
the spfile.
initmyrac1.ora -> SPFILE=/u02/oracle/dbs/spfileMYRAC.ora
initmyrac2.ora -> SPFILE=/u02/oracle/dbs/spfileMYRAC.ora

Now connect to each instances specifically and start the database:-
NODE1:
export ORACLE_SID=MYRAC1
sqlplus / as sysdba
startup;

NODE2:
export ORACLE_SID=MYRAC2
sqlplus / as sysdba
startup;

SQL>select * from v$active_instances;–this should display 2 nodes.

Note
You can also use dbca to create your database as DBCA is rac aware.

Oracle clusterware is a required component for using RAC. We can use other clusterware from vendors if it is certified. Oracle Clusterware | / \ Voting Disk OCR A RAC database can have upto 10 Instances. Tools for RAC Are:-
Enterprise Manager

Cluster Verification Utility CVU

Server control SRVCTL

Cluster ready services control CRSCTL

Oracle Interface config tool OIFCFG

OCR Configuration Tool OCRCONFIG