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Demystifying Oracle RAC Internals
Barb Lundhild RAC Product Management
The following is intended to outline our general
product direction. It is intended for information purposes only, and may not be incorporated into any
contract. It is not a commitment to deliver any
material, code, or functionality, and should not be
relied upon in making purchasing decisions.
The development, release, and timing of any features or functionality described for Oracle’s
products remains at the sole discretion of Oracle.
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Agenda Answer most common questions about Oracle Clusterware and Oracle RAC
• Architecture
• Oracle Clusterware – Group Membership
• Oracle Cluster Registry
• The Interconnect
• The Public Network and the Virtual IP (VIP)
• Oracle RAC Startup/Shutdown
• Advanced Features of Oracle RAC
• Appendix
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Architecture
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Service
RAC Architecture
public network
Node1
Operating System
Oracle Clusterwarecluster
interconnect
instance 1
ASM
Node n
Operating System
Oracle Clusterware
instance n
ASM
Redo / Archive logs all instances
shared storage
Database / Control files
OCR and Voting Disks
VIP1 VIPn
Managed by ASM
RAW Devices
Listener Listener
Service
What does Clusterware provide?
Operating System
Group Membership
High Availability
Framework
Process Monitor
VIP
Event Management
Oracle
Clusterware
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Oracle Clusterware Architecture
Operating System
CSS
CRS
OPROC
VIP
RACG
EVM
Oracle
Clusterware
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Oracle Clusterware
Group Membership and Heartbeats
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Oracle Clusterware Group Membership and Heartbeats
• Cluster needs to know who is a member at all times
• Oracle Clusterware has 2 heartbeats:
• Network heartbeat
If a node does not send a heartbeat for MissCount (time in
seconds), then node is evicted from cluster
• Disk heartbeat
If disk heartbeat is not updated in I/O timeout, then node is
evicted from cluster
Oracle Clusterware Split Brain Resolution
• When interconnect breaks – keeps the largest cluster
possible up, other nodes will be evicted, in 2 node cluster lowest number node remains.
• IO Fencing similar to the Stonith algorithm
• Voting disk is used to detect network problems that could
lead to a split-brain
• Final arbiter of the status of configured nodes, either up or down,
and delivers eviction notices
• Recommended to have at least 3 voting disks
• Standard NFS support for 3rd voting disk on Linux, AIX, or Solaris
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IT IS NOT SUPPORTED TO
REDUCE MISSCOUNT BELOW
THE DEFAULT (30s)
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Oracle Cluster Registry
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Oracle Cluster Registry (OCR)
• A repository containing the definition of the
configuration of the cluster and status of resources managed by the cluster
• Required file(s) for Oracle Clusterware
• Initialized during install of Oracle Clusterware
• Location defined in Registry on Windows or OCR.LOC on
Linux and Unix
• Mirrored by Oracle Clusterware or externally (RAID)
• Supports both automatic (every 4 hours) and manual
(new in 11.1) backups
• ocrconfig –manualbackup
Oracle Cluster Registry (OCR)
• Tools to manage OCR
• OCRCONFIG – command line tool to manage backups,
restore, import, export, repair, and replace
• Make sure you have a good backup before changing the
cluster configuration!
• OCRCHECK – checks integrity and displays the version of
the OCR's block format, total space available, used space,
and the OCR locations that you have configured
• OCRDUMP - view the OCR contents by writing OCR content to a file or stdout in a readable format.
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InterconnectFailure Protection and Scalability
Service
Private Interconnect
public network
Node1
Operating System
Oracle Clusterware
cluster
interconnect
instance 1
ASM
VIP1
Listener
Node 2
Operating System
Oracle Clusterware
instance 2
ASM
VIP2
Listener
Service
Switch 1 Switch 2
Node n
Operating System
Oracle Clusterware
instance n
ASM
VIPn
Listener
Service
/…/
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The Interconnect
• Interconnect is typically a standard GigE network
• IP over IB is supported
• Network should use a private dedicated non-routable switch or VLAN
• A crossover cable is not supported as an interconnect
• For high availability and scalability use OS based
solution to combine multiple physical links into a single logical link
• Same technology can be applied to public network
• Only logical link should be provided to Oracle
Clusterware and therefore Oracle RAC
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Public Network and VIPFailure Protection
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Why Oracle RAC has a VIP?
• Protects database clients from long TCP/IP timeouts
(can be >10 minutes)
• During normal operation, works the same as
hostname
• During failure, it removes network timeout from
connection request time, client fails immediately to
next address in the list
sales.us.acme.com =(DESCRIPTION=(ADDRESS_LIST=
(LOAD_BALANCE=on)(FAILOVER=ON)
(ADDRESS=(PROTOCOL=tcp)(HOST=sales1-vip)(PORT=1521))
(ADDRESS=(PROTOCOL=tcp)(HOST=sales2-vip)(PORT=1521)))
(CONNECT_DATA=
(SERVICE_NAME= sales.us.acme.com)))
Oracle RAC VIPThe Details
• One for each node in cluster
• Required for Oracle Clusterware installation
• IP and network name should not currently be in use
• Should be registered in DNS and must be on the same
subnet as public IP address
• Configuration managed by VIPCA and SRVCTL
• Note that netmask defaults to 255.255.255.0, rather
than defaulting to netmask of underlying physical
interface.
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Oracle RAC VIP is DIFFERENT
• Only accepts connections when on its home node
• Failure on home node: relocates to another node in the
cluster only to send a error back to client (it will not be
in the listener so connections are not accepted!)
• You will only have one active RAC VIP per node (there
may be others who have relocated due to failure!)
• Independent of number of databases running in cluster
Oracle RAC VIP
[root@pmrac1 root]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:12:79:D8:90:93
inet addr:144.15.214.10 Bcast:144.15.215.255
Mask:255.255.252.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5070815 errors:0 dropped:0 overruns:0 frame:0
TX packets:3064435 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:509963813 (486.3 Mb) TX bytes:3621223517 (3453.4 Mb)
Interrupt:25
eth0:1 Link encap:Ethernet HWaddr 00:12:79:D8:90:93
inet addr:144.15.214.30 Bcast:144.15.215.255
Mask:255.255.252.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5762695 errors:0 dropped:0 overruns:0 frame:0
TX packets:5679252 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:3400642002 (3243.1 Mb) TX bytes:3166774792 (3020.0 Mb)
Interrupt:25
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Listener.ora
SID_LIST_LISTENER_PMRAC1 =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /u01/oracle/product/10gR2/asm)
(PROGRAM = extproc)
)
)
LISTENER_PMRAC1 =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = pmrac1-vip)(PORT = 1521)(IP = FIRST))
(ADDRESS = (PROTOCOL = TCP)(HOST = 144.25.214.45)(PORT = 1521)(IP = FIRST))
)
)
Use the VIP in the Address List Automatically completed by DBCA
• init.ora remote_listener = listeners_sales
local_listener = listeners_sales1
• tnsnames.ora in RAC ORACLE_HOMELISTENERS_SALES =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = node3-vip)(PORT = 1521))
)
LISTENERS_SALES1 =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip)(PORT = 1521))
)
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Application VIPs
• New resource as of Oracle RAC 10g Release 2
• Created as functional VIPs which can be used to connect to an application regardless of the node it is
running on
• VIP is a dependent resource of the user registered
application
• There can be many VIPs, one per User Application
Creating an Application VIP
• The usrvip script must run as root
• The default permissions need to be changed after registration
• As root…
crs_setperm ApplicationVIP1 –o root
• Allow oracle user to execute this script
• As root…
crs_setperm ApplicationVIP1 –u user:oracle:r-x
• Start the VIP
• As oracle…
crs_start ApplicationVIP1
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Oracle RACStartup/Shutdown
Node Startup Sequence
Service
Operating System
Oracle Clusterware
Instance 1
ASM
VIP1
Listener
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VIP1
Oracle Dependencies
public network
Node1
cluster
interconnect
Node 2
Operating System
Oracle Clusterware
instance 2
ASM
Redo / Archive logs all instances
shared storage
Database / Control files
OCR and Voting Disks
VIP2
Managed by ASM
RAW Devices
Service
Operating System
Oracle Clusterware
instance 1
ASM
VIP1
Listener Listener
Service
Listener
Oracle DependenciesPrior to 10.2.0.3
public network
Node1
cluster
interconnect
Node2
Operating System
Oracle Clusterware
instance 2
ASM
Redo / Archive logs all instances
shared storage
Database / Control files
OCR and Voting Disks
VIP2
Managed by ASM
RAW Devices
Service
Operating System
Oracle Clusterware
instance 1
ASM
VIP1
Listener Listener
Service
VIP1
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Advanced Features of RACHigh Availability and Load
Balancing for Applications
Services
• Application workloads can be defined as Services• Individually managed and controlled
• Assigned to instances during normal startup
• On instance failure, automatic re-assignment
• Service performance individually tracked
• Finer grained control with Resource Manager
• Integrated with other Oracle tools / facilities (E.G. Scheduler,Streams)
• Managed by Oracle Clusterware
• Several services created and managed by database server
Many features discussed do not apply to default database service
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Cluster Managed Services
• Service has a set of resources defined to Oracle
Clusterware
• Oracle Clusterware manages start/stop/re-locate
based on definition
• Define Preferred (normal operations) and Available (if
failure occurs) instances
• Dependent on Instance and VIP
• Manage using Enterprise Manager
• SRVCTL CLI for Cluster configuration
• DBMS_SERVICE PL/SQL package
What is FAN?
• Fast Application Notification (FAN) is a RAC
notification mechanism
• FAN HA Events: Notification of Up/Down for service,
instance & node
• Load Balancing Advisory Events: Advise clients of
current load for service and where to send connection requests
• Enable it, and Forget it.
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Oracle Notification Service (ONS)
• Publish/Subscribe Messaging System
• Allows both local and remote consumption
• Used by Fast Application Notification (FAN) to publish
HA Events and Load Balancing Events
• Used by FAN clients to subscribe to events
• Automatically installed and configured by the installation of Oracle Clusterware
• DO NOT TURN OFF – Required by Oracle
Clusterware and RAC
Fan Clients
• HA Events: JDBC Implicit Connection Cache, OCI,
ODP.NET Connection Pools, Listener, Server Side Callouts, CMAN
• Load Balancing Advisory Events: JDBC Implicit
Connection Cache, ODP.NET Connection Pools, Listener, CMAN
• New with 11.1.0.7: Universal Connection Pool for
JAVA
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Fast Connection Failover
• Fast and reliable high availability for connections in an
Oracle Real Application Clusters 10g environment
• Enable it and forget it
• Application can make it transparent to user by trapping SQL Exception and retrying
• Supported by Oracle JDBC, OCI, and ODP.NET
Load Balancing Advisory
• Load Balancing Advisory is an advisory for balancing
work across RAC instances.
• Load Balances at the transaction level (not
connections!)
• Directs work to where services are executing
well and resources are available.
• Adjusts distribution for different power nodes,
different priority and shape workloads, changing
demand.
• Stops sending work to slow, hung, failed nodes
early.
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Runtime Connection Load Balancing
• When application does “getConnection”, the connection given is the one that will provide the best service.
• Supported by Oracle JDBC, OCI, and ODP.NET connection Pools
• Policy defined by setting GOAL on Service
• Need to have Oracle Net Services Connection Load Balancing
Web ClientWeb Client
RAC
Database
Instance1
Instance2
Instance3
Pool
Affinity Context
Connection
Leverage Temporal Connection AffinityNew with 11.1.0.7
Connect to me
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Leverage XA Connection AffinityNew with 11.1.0.7
• DB 11g fixes the correctness problem. XA Affinity
adds Performance and Scalability.
• Eliminates current single DTP service limitation for
XA/RAC
• XA affinity is the ability to automatically localize a
global transaction to a single RAC instance
• Scope is the life of a global transaction
• First connection request for a global transaction uses
Runtime Connection Load Balancing (RCLB)
• Subsequent requests use affinity and are routed to the
same RAC instance where XA first started
AQ&Q U E S T I O N SQ U E S T I O N S
A N S W E R SA N S W E R S
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Appendix
For More Information
http://search.oracle.com
or
otn.oracle.com/rac
REAL APPLICATION CLUSTERS
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Useful Metalink Notes
• Note 342082.1 “How to Change Subnet Masks for VIPs”
• Note 294430.1 “CSS Timeout Computation in RAC 10g ”
• Note 284752.1 “10g RAC: Steps To Increase CSS Misscount,
Reboottime and Disktimeout”
• Note 291962.1 ‘Setting Up Bonding in SLES 9’
• Note 291958.1 ‘Setting Up Bonding in Suse SLES8’
• Note 298891.1 ‘Configuring Linux for the Oracle 10g VIP using
bonding’
• Note 283107.1 ‘Configuring Solaris IP Multipathing (IPMP) for
the Oracle 10g VIP’
OTN.ORACLE.COM/RAC
• Workload Management with Oracle Real Application
Clusters (FAN, FCF, Load Balancing)
• Using standard NFS to support a third voting disk on a
stretch cluster configuration on Linux
• Using Oracle Clusterware to Protect 3rd Party
Applications
• New: otn.oracle.com/clusterware
• RAC Sample Code Pagehttp://www.oracle.com/technology/sample_code/products/rac/index.html
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