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Table of Contents
RAC
Oracle RAC Overview
Real Application Clusters (RAC) is an clustering solution whereby multiple Oracle instances can communicate with one database located on shared storage.<br /> Datafiles and controlfiles are shared but each instance will have its own redo log files and undo tablespace.<br /> Use crsctl to manage the clusterware<br /> Use srvctl to manage the cluster<br /> <br />
Know nothing about RAC? Go through the RAC Attack labs step-by-step installation for 11g RAC_Attack!<br /> or 12c RACAttack for an excellent (hands on) introduction.<br />
How to Backup and Restore a RAC Database
RAC components
Virtual IP
A virtual IP address is an IP address setup to “float” between the real IP addresses associated with each instance in the cluster. If the IP address assigned to the virtual IP becomes unavailable, the IP address from the still available instance will be assigned to the virtual IP thus maintaining database availability for the users.
Voting Disk
A Voting Disk is a file on a shared filesystem. It maintains a list of available cluster nodes and can resolve split-brain scenarios.<br /> All instances write to the voting disk to indicate that they are still active.
Cluster Registry
The Cluster Registry (OCR) is used to store cluster wide settings and status information such as node names, IP and VIP addresses, voting disk locations, node applications, database names, instance names, listener names, etc.
Clusterware processes
A RAC cluster consists of the following daemons<br />
- crsd – Cluster Resource Services Daemon
- cssd – Cluster Synchronisation Services Daemon
- evmd – Event Manager Daemon
RAC commands
Location of Oracle Local Registry configuration file (olr.loc)
This file points to the clusters local node repository and depending on the OS, it is in one of these 2 locations
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This file is managed by OHASD and will point to the olrconfig_loc and the crs_home
Location of cluster config files
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Some cluster control commands to check the status / health of the clusterware
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List network interfaces available to this cluster node
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Is Oracle Restart (High Availability Service) enabled?
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Is ASM autostart enabled?
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Are diskgroups registered?
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Is database registered and autostart enabled?
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if not…
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Set ASM diskgroups to be used by database
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Stop and start the clusterware services
To set the correct home, can also search /etc/oratab for the relevant ASM instance and use . oraenv
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Prevent cluster services from starting up on boot
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Re-enable clusterware services
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List the resources under cluster control
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or
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Find the ORACLE_HOME from a database cluster metadata file
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Stop all the cluster resources for a particular ORACLE_HOME
If all resources for a home need to go down (e.g. for patching), this should do it.<br /> Save the state so that the start command knows what to start and what not to.
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Before running the startup, the state file can be edited and instances added/removed as it is a simple text file
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General syntax for starting and stopping a RAC instance
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Stop one instance of a RAC database
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Start an ASM instance on a specific node
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Stop all instances of a RAC database
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Start all instances of a RAC database
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Start a database in mount mode
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Stop ASM on a RAC node
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Start / Stop all node applications on a RAC node
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Start / Stop a listener on a RAC node
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Start / Stop services on a RAC node
srvctl stop database command implicity does a srvctl stop services (because services are dependent on database).<br /> However, a subsequent srvctl start database requires an explicit srvctl start service
- service name list is optional and if not provided, the SRVCTL starts all of the database's services<br />
- -c connect_str Connect string (default: / as sysdba)<br />
- -q Query connect string from standard input
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Status of an ASM instance on a RAC node
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Status of the database, all instances and all services
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Status of named instances with their current services (if on local node)
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Add a new node
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Add a new database
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Add named instances to an existing database
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Add a service to an existing database with preferred instances (-r) and available instances (-a). Use basic failover to the available instances
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Add a service to an existing database with preferred instances (-r) and available instances (-a). Use preconnect at the available instances
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Remove the applications for a database
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Remove the applications for named instances of an existing database
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Remove the service
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Remove the service from the instances
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Remove all node applications from a node
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Modify an instance to execute on another node
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Modify a service to execute on another node
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Modify an instance to be a preferred instance for a service
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Relocate a service from one instance to another
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Switchover / failover a database from one node (server) to another
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Enable CRS resources (resources can be up or down when these commands are issued)
Enable the database
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Enable the named instances
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Enable the service
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Enable the service at the named instance
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Disable CRS resources (resources must be down when these commands are issued)
Disable the database globally
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Disable the named instances
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Disable the service(s) globally
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Disable the service on the named instance
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Status of a named services
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Status of all nodes supporting database applications
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How to tell if database is a RAC cluster
This will be TRUE if RAC database
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or, the GV$ views will show more than 1 record
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or
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or
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or
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Show session distribution across the RAC nodes
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