This document summarizes a presentation on Oracle RAC (Real Application Clusters) internals with a focus on Cache Fusion. The presentation covers: 1. An overview of Cache Fusion and how it allows data to be shared across instances to enable scalability. 2. Dynamic re-mastering which adjusts where data is mastered based on access patterns to reduce messaging. 3. Techniques for handling contention including partitioning, connection pools, and separating redo logs. 4. Benefits of combining Oracle Multitenant and RAC such as aligning PDBs to instances. 5. How Oracle In-Memory Column Store fully integrates with RAC including fault tolerance features.

2. Understanding Oracle RAC (12.1.0.2) Internals: The Cache Fusion Edition
Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |
Markus Michalewicz
Director of Product Management
Oracle Real Application Clusters (RAC)
October 1st, 2014
@OracleRACpm
http://www.linkedin.com/in/markusmichalewicz
http://www.slideshare.net/MarkusMichalewicz

3. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Safe Harbor Statement
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.
3

4. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
4
The Secret to the Scalability of Any System – A straight vertical line
Simplification 1
Simplification 2

5. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
5
Three Alternative Architectures – The Same Idea Applies

6. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
6
Three Alternative Architectures – The Same Idea Applies

7. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
7

8. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
8

9. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• Requester
• Listener
• Service
• Holder
• Master
• Session PQ/PX:
9
Oracle RAC Combines it All & Adds Services
Instance
Block, unless otherwise stated.

10. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• In an Oracle environment, listeners establish connections with an instance.
• In an Oracle RAC environment two types of listeners are used (for this purpose):
1.SCAN and SCAN Listener
2.Local Listeners per node
•Services are used to load balance work.
•Local listeners will establish connections on instances where the service is offered.
•Once a session is established within an instance, the sessions stays until closed.
10
Listeners and Services Direct Work to an Instance

11. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• Local Cache Hit
• Access time: nanoseconds
11
• Remote Cache Hit
• Access time: microseconds
• Data is on disk
• Flash cache access time: microseconds
• Disk controller cache: access time: micros.
• Spinning disk access time: milliseconds
Getting Access to Data
Whether local or remote, cache hits are always faster than reading from spinning disks

12. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Case 1 (all local)
• All entities in one instance
• Data holding instance
• Session “holding” instance
• Mastering Instance
12
Case 2 (local / remote)
• Some entities in one instance
•Data holding instance
• Session “holding” instance
• Two way communication
Case 3 (all distributed)
• All entities are dispersed
• Three way communication
to obtain a given block of data
• Message operations have been subject to
improvements since Oracle RAC 10g times.
Maximum Three Way Communication
write write write
Message Message
Block

13. Copyright © 2014, Oracle and/or its affiliates. All rights reserved. 13
Dynamic Retrieval of Data
+ +
2
3
1
• In order to fulfill a given request,
Oracle RAC can decide to:
• Assemble data spread across instances and disks
• Perform a (full) disk read for (parts of) the data
• Use assembly and (full) disk reads dynamically
• The decision which access path to use is
dependent on various factors (e.g. IO capacity,
network utilization)
• Respective parameters are monitored
• The access path can change
accordingly and dynamically.
Once data has been shipped to an instance, it resides in
the cache for further (local) access. Updates will be
communicated as required (via messages).

14. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
14

15. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• In Oracle RAC, every object is mastered (as part of Global Cache Services / GCS) by an instance.
• The Global Resource Directory (GRD) is used to “keep track” of mastering.
• Illustration above is symbolic for this matter.
15
• If a session requests write access to a block that is not mastered by the instance hosting the session, the master instance needs to be contacted (via message).
• Based on user access patterns, a Dynamic Re-Mastering (DRM) can be triggered, changing the master for an object from one instance to another.
• Relocating the master to the instance where data is requested most reduces the messaging.
Mastering and Dynamic Re-Mastering
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
brazil
Oracle GI | HUB
Oracle RAC
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
brazil
Oracle GI | HUB
Oracle RAC
write
write
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
brazil
Oracle GI | HUB
Oracle RAC

16. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• DRM is used internally and externally.
• Externally means access patterns can influence the mastering of user data.
• Internally DRM is used for the management of UNDO data across instances for example.
• DRM activity is also performed upon instances leaving or joining the cluster.
• Do not turn DRM off (_gc_policy_time=0)!
• Optimize _gc_policy_minimum to run / trigger DRM at a convenient moment under normal operations.
• Consider using smaller SGA sizes.
• See MOS note 1619155.1 – “Best Practices and Recommendations for RAC databases using SGA larger than 300GB” as applicable
• “dbms_cacheutil” can be used to manually set and release affinity under well understood circumstances.
16
Dynamic Re-Mastering (DRM) – Recommendations
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
brazil
Oracle GI | HUB
Oracle RAC
write

17. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• The Cache Fusion Accelerator (CFA) is an
• OS kernel (Linux & Solaris only) module
• which can respond directly to certain lock requests via RDSv3.
• The lock state is saved in memory shared by the database and the kernel.
• CFA saves user/kernel context switches, frees up CPU cycles in LMS, and “speeds up” messages.
• CFA will be activated on Engineered Systems over time, including the Oracle Database Appliance.
• CFA contributes to a better, linear scaling.
• CFA is one of a long list of improvements.
17
New in 12.1.0.2: Cache Fusion Accelerator
germany
Oracle GI
Oracle RAC
argentina
Oracle GI
Oracle RAC
brazil
Oracle GI
Oracle RAC
write
LMS process
Accelerator
Lock grant

18. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
18
New in 12.1.0.2: Cache Fusion Accelerator
germany
Oracle GI
Oracle RAC
argentina
Oracle GI
Oracle RAC
brazil
Oracle GI
Oracle RAC
write
LMS process
Accelerator
• The Cache Fusion Accelerator (CFA) is an
• OS kernel (Linux & Solaris only) module
• which can respond directly to certain lock requests via RDSv3.
• The lock state is saved in memory shared by the database and the kernel.
• CFA saves user/kernel context switches, frees up CPU cycles in LMS, and “speeds up” messages.
• CFA will be activated on Engineered Systems over time, including the Oracle Database Appliance.
• CFA contributes to a better, linear scaling.
• CFA is one of a long list of improvements.

19. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
19

20. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
write
write
• Contention can occur in any multi- user system (even in SI databases)
• User data as well as “metadata” (e.g. an index) can be subject to contention
20
• You can still guide users to only one instance in an Oracle RAC environment.
• As soon as you scale out, contention can occur between instances (not only within an instance).
• From a contention perspective, a 2-node setup is basically the same as a 3 or more nodes setup.
• The difference is in the required message- based communication to obtain a block considering the mastering.
How To Handle Contention – Basics
write
write
write
write
write
write
write
write
write
write
write
write
Note: for scalability, only write/write contention needs to be considered.

21. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• Frequent transactional changes to the same data blocks in all instances may result in “write hot spots”.
• Block with pending changes may be “pinged” by other instances.
21
• Pending redo must be written to log before the block can be transferred
• Latency for a deferred block transfer becomes dependent on delay for log IO
• Contention can affect related data as much as it can affect the actual “user data”.
• Right growing indexes and index contention are common.
• In 99% of OLTP performance issues, write hot spots occur on indexes.
How To Handle Contention – Considerations
write
write
write
write
write
write
write
write
Sequence
write
write
write
write
REDO

22. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• Avoid frequent transactional changes to the same data blocks in all instances using partitioning and services.
• Logically partition data so that sub- data is handled in one instance only. Guide users via services accordingly.
22
• Place redo logs on fast storage if performance critical; e.g. SSDs
•Implemented in 11.2.2.4 of Exadata and Oracle Database Appliance by default (Smart Logs and SSDs, respectively)
•Separate disks for logs from other IO busy disks
• Use either for better cache locality:
• Global hash partitioned indexes
• Locally partitioned indexes
• Drop unused indexes
How To Handle Contention – General Solutions
write
write
write
write
Sequence
write
write
write
write
REDO
write
write
write
write
Get the best out of Oracle Partitioning - A practical guide and reference https://www.slideshare.net/secret/nHJV1CjWWOlGOl

23. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• UCP supports “Connection Affinity”:
• Transaction-Based Affinity
• Web Session Affinity
http://docs.oracle.com/database/121/JJUCP/rac.htm#JJUCP8197
23
• Connection Pools limit the number of connections to the database – example:
• Oracle Universal Connection Pool (UCP)
• Use “Database Resident Connection Pooling” when no. of active sessions much smaller then no. of open session.
• Fast Application Notification (FAN) – enabled connection pools receive Load Balancing information based on the Workload Repository and on a per-service basis.
How To Handle Contention – Use Connection Pools
write
write
write
write
write
write
Connection Pool
Connection Pool
Connection Pool
busy
idle

24. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
24

25. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
•Pluggable Databases (PDBs) represent themselves as services in an Oracle RAC Multitenant Database, ensuring extremely fast failover.
• PDBs can be used to conveniently align users to instances with all the benefits, providing higher consolidation benefit and agility.
25
• Oracle RAC Multitenant Databases help to consolidate.
• Future improvements will ensure greater efficiency.
• Multithreaded Redo Log writer already implemented.
Oracle Multitenant and Oracle RAC – a Symbiosis
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
cons_1
cons_2
REDO

26. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
•Pluggable Databases (PDBs) represent themselves as services in an Oracle RAC Multitenant Database, ensuring extremely fast failover.
• PDBs can be used to conveniently align users to instances with all the benefits, providing higher consolidation benefit and agility.
26
Oracle Multitenant and Oracle RAC – a Symbiosis
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
cons_1
cons_2
REDO
• Oracle RAC Multitenant Databases help to consolidate.
• Future improvements will ensure greater efficiency.
• Multithreaded Redo Log writer already implemented.
• Per-PDB/service optimized GCS operations coming in future.
More information, see: Oracle Multitenant meets Oracle RAC - http://www.slideshare.net/MarkusMichalewicz/oracle- multitenant-meets-oracle-rac-ioug-2014-version

27. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Program Agenda
1
2
3
4
5
Cache Fusion Overview
(Dynamic Re-) Mastering
Handling Contentions
RAC Meets Multitenant
RAC Meets In-Memory
Oracle Confidential – Internal/Restricted/Highly Restricted
27

28. Copyright © 2014, Oracle and/or its affiliates. All rights reserved. 28
Oracle In-Memory and Oracle RAC
Breakthrough:
Dual Format
Database
Generate
Reports
Instantly
Column
Store
Replaces
Analytic
Indexes
In-Memory
Column Store
Full HA &
Integration
with
Industry
Standards

29. Copyright © 2014, Oracle and/or its affiliates. All rights reserved. 29
Oracle In-Memory and Oracle RAC – A Dream-Team
In-Memory
Column Store
Addresses
Addresses
Breakthrough:
Dual Format
Database
Column
Store
Replaces
Analytic
Indexes

30. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
“Full support for RAC scale-out means Oracle Database In-Memory can be used on our largest Data Warehouse, enabling more near real-time analytics.”
–Sudhi Vijayakumar, Senior Oracle DBA Yahoo Inc.
30

31. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
Oracle Database In-Memory: Unique Fault Tolerance
•Similar to storage mirroring
•Duplicate in-memory columns on another node
•Enabled per table/partition
•Application transparent
•Downtime eliminated by using duplicate after failure
31
Only Available on Engineered Systems

32. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
“Downtime is extremely costly for our business. Oracle’s In-Memory architecture takes the right approach to balancing real-time speed with continuous availability.”
–Jens-Christian Pokolm Analyst IT-DB Architecture & Engineering Postbank Systems AG
32

33. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
• In-Memory compresses data,
optimizing the use of memory.
• Memory allocated for In-Memory
is subject to simplified lock mgmt.
33
• In-Memory Speed and Capacity of
Low Cost Disk
• PCI Flash works mostly locally.
• Shared solutions require
RAC external synchronization.
• Coming soon on ODA: a fully
integrated shared flash cache.
Optimized Used of Memory in Every Layer
Normal
Buffer Cache
In-Memory
Format
Normal
Buffer Cache
In-Memory
Format
• Compressed
• Lock mgmt.
simplified
germany
Oracle GI | HUB
Oracle RAC
argentina
Oracle GI | HUB
Oracle RAC
brazil
Oracle GI | HUB
Oracle RAC
? ? ?
Coming soon…

34. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
•Database and Middleware streams available
•Videos
–Feature different groups and presenters
–Cover a broad range of topics and products
•FREE OF CHARGE Oracle RAC PM / Dev contributions:
– Oracle Flex Cluster: Optimized Resource Management for the Cloud - Ian Cookson
– Oracle Grid Infrastructure 12c Bundled Agents – Shankar Iyer
– ACFS Product Overview and Use Cases - Ara Shakian
– The Oracle Real Application Clusters (RAC) Family of Solutions - A User Guide – Markus Michalewicz
– Next Generation Oracle Automatic Storage Management - Jim Williams
– Implementing DBaaS with Oracle RAC 12c and Quality of Service Management - Mark Scardina
– Oracle RAC Practical Performance Management and Tuning – Markus Michalewicz
Oracle Learning Streams: http://education.oracle.com/streams/

35. Copyright © 2014, Oracle and/or its affiliates. All rights reserved.
36