Oracle RAC

1
Oracle RAC

• Overview of Real Application Clustering Features
  and Functionality

2
Overview

• What is RAC?
• Cache Fusion
• Failover and Load-balancing
• Transparent Application Failover (TAF)
• Other RAC Features

3
RAC What is it?

• Multiple instances of Oracle running on up to 8
  nodes
• Multiple instances share a single physical
  database
• All instances can simultaneously execute
  transactions against the single database
• Caches are synchronized using Oracles Global
  Cache Management technology (Cache Fusion)

4
History of Oracle RAC

• Previous Oracle Clustering Products
• Oracle FailSafe on Windows
• OPS (Oracle Parallel Server) on multiple
  platforms
• OPS to RAC 7.3 OPS ? 8i OPS ? 9i RAC ? 10g RAC
• The clustering mechanism used to be more
  dependent on the Operating System.
• With 10g RAC, clustered database is built into
  Oracle

5
Oracle RAC Features

• Full Cache Fusion
• Enhanced coordination of cache management and
  distributed lock manager (DLM)
• Lock simplification and automation
• Global Cache Service coordinates local buffer
  cache and remote block transfers
• Enhanced IPC
• Resource configuration simplification and
  automation
• Improved cluster aware tools
• Enhanced DBCA
• Oracle Enterprise Manager and Grid Control
  Integration Enhancements

6
RAC uses Shared Everything
Users
Database
7
How RAC clustering is done

• One set of data
• All nodes in the cluster see the same set of data
• All nodes have access
• Any node can update the data

8
Increased Manageability

• One virtual system to configure and manage
• Single Oracle Database
• Single management console
• Single system image for the database integrated
  with the cluster
• Cluster-wide monitoring and diagnostics
• Oracle Enterprise Manager Integration (9i)
• Oracle DBConsole and Grid Control Integration
  (10g)

9
Whats shared Whats not

• Shared
• Disk access
• Resources that manage data
• All instances have common data controls files
• Not Shared
• Each node has its own dedicated
• System memory
• Operating system
• Database instance
• Application software
• Each instance has individual
• Log files and
• Rollback segments

10
RAC can perform

• Load-balancing
• Failover

11
Load-Balancing through the Listener
Listener
Listener
Listener
Listener
Database
12
How workload is balanced

• Nodes report CPU usage to listeners

Node 1
Database
13
How workload is balanced

• Listeners choose least busy node when request
  comes in from client

Node 1
Database
14
Load-Balancing
Users
Database
15
Failover

• If a node in the shared disk cluster fails, the
  system dynamically redistributes the workload
  among the surviving cluster nodes.
• RAC checks to detect node and network failures.
  A disk-based heartbeat mechanism uses the control
  file to monitor node membership and the cluster
  interconnect is regularly checked to determine
  correct operation.
• Reduced time to recovery with concurrent resource
  configuration and instance (cache) recovery
• Enhanced failover reliability in 10g with the use
  of Virtual IP addresses (VIPs)

16
Failover
Users
X
Database
17
Transparent Application Failover

• Masks failures to end users they dont need to
  log back into the system
• Applications and users are transparently
  reconnected to another node
• Applications and queries continue uninterrupted
• Transactions can failover and replay
• Login context maintained
• DML transactions are rolled back

18
RAC Improvements for Oracle 9i

• Full Cache Fusion
• Enhanced coordination of cache management and
  distributed lock manager (DLM)
• Lock simplification and automation
• Global Cache Service coordinates local buffer
  cache and remote block transfers
• Enhanced IPC (InterProcess Communication)
• Resource configuration simplification and
  automation

19
Oracle 10g RAC New Features

• Integrated Clusterware Management
• No third-party clusterware software required
• Automatic Workload Management
• Application workloads can be managed through
  named services
• Single System Image Management
• Enterprise Manager manages RAC instances as a
  single image
• Fast Connection Failover
• Fast recovery between the database and mid-tier
  applications
• Performance Improvements
• Reduced message traffic, memory usage, and other
  resources
• Zero Downtime Patching
• Patches may be applied one node at a time without
  downtime
• Cluster Verification and Improved Diagnostic
  Tools
• New cluster diagnostic tool and improved
  diagnostic tools

20
Full Cache Fusion

• Is a major feature of RAC starting with 9i
• The underlying technology that enables RAC
• Protocol that allows instances to combine their
  data caches into a shared global cache
• Allows any node to get the most up-to-date data
  information from the cache of any other node in
  the cluster without having to access the disk
  drives again.
• Improved performance with 10g

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What is Cache Fusion? When do I care about it?

• Dirty block of data is created
• Data from disk is read into memory on a node
• Data is updated on that node
• Data hasnt been written to disk yet.
• Another node requests the data

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ABC block of data written to the disk drives in
the database
Node A
Node B
ABC Data
23
ABC block of data read into memory on Node A
Node A
Node B
ABC Data
ABC Data
24
ABC updated to XYZ in cache
Node A
Node B
ABC Data
XYZ Data
ABC Data
25
Node B requests data block
I want data! Gimme! Gimme!
Node A
Node B
ABC Data
XYZ Data
ABC Data
26
Node A must write data block to disk drive
I want data! Gimme! Gimme!
Node A
Node B
ABC Data
XYZ Data
Previous to 9i RAC
write
ABC Data
XYZ Data
27
Node B must read data block from disk drive
Node A
Node B
ABC Data
XYZ Data
XYZ Data
Previous to 9i RAC
read
ABC Data
XYZ Data
28
Now with RAC Cache Fusion
I want data! Gimme! Gimme!
Node A
Node B
ABC Data
XYZ Data
XYZ Data

• Data is transferred immediately via the
  interconnect
• Shared cache minimizesslow I/O

ABC Data
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Shared Cache Across Nodes
Users
Database
30
Resource Simplification and Automation

• No init.ora parameters required
• Resource affinity
• to move the location of the resource masters for
  a database file to the instance where block
  operations are most frequently occurring. This
  optimizes
• Dynamic resource remastering
• Ability to move the ownership of a resource
  between instances of Real Application Clusters.
• Dynamic resource remastering is used to implement
  resource affinity for increased performance.

31
Review

• What does cache fusion avoid that was mandatory
  in previous versions of Oracle Parallel Server?
• Which Oracle process is most important in
  managing user session failover?
• If the purpose of the interconnect is NOT to
  serve as a heartbeat, where is the heartbeat?

32
Summary

• New Features
• Shared Everything Clustering
• Cache Fusion
• RAC Clustering failover load-balancing