1. Oracle Database 12c
Whats New…

2.  Navneet Upneja (Manager, Database & Applications)
 9 Years of Experience in Oracle Databases, OBIEE,
Informatica, ODI etc…
 Oracle Certified Professional
 Hand on experience on OLTP, Datawarehouse, Oracle
BI, APEX…
Co-Founder of AIOUG - North India Chapter.
Email: navneetupneja@gmail.com
Blog: http://navneetupnejadba.wordpress.com/
Twitter: @navneetupneja
Presentations: http://www.slideshare.net/navneetupneja
Navneet UpnejaNavneet Upneja

3. Overview
• Multi-Tenant Architecture
• Threaded Execution
• Online Optimizer Statistics
• GTT Statistics
• Global Temporary Table Undo
• Invisible Columns
• Multiple Indexes
• ILM
• DDL Logging
• Limit on PGA
• Moving Datafile Online
• Q&A

4. Multitenant Architecture
• Oracle 12c – “c” for “Consolidation”
– New concept of Container Database (CDB)
– Multiple databases can be part of one CDB
– Each Database is called “PDB”
– CDB contains:
• Root Container (CDB$ROOT) : Master Datafiles and Metadata
• Seed Container (PDB$SEED): Template to create new pdb.
• Pluggable Database (PDB): One or more PDB’s
• New “CDB_..” dictionary views.

5. Threaded Architecture
• Pre 12c and Default in 12c
– Windows: Threaded Model (Only one process “oracle.exe”)
– Unix: Independent Process for each Oracle Process.
– “threaded_execution” – New in 12c
– Default to “False”.
– Require reboot of instance
– Login using “sys” Require password file after this change
– 1 Process will have multiple sub-processes called “Threads”
– DEDICATED_THROUGH_BROKER_LISTENER=ON
– New columns added to “V$Process” table.
• STID – Thread Number
• SOSID – Concatenation of Process and Thread
• New entry in Execution type as “THREAD”
– PMON, VKTM, PSP0, DBW0.. , will be still implemented as before
– Useful towards achieving “Consolidation”.

6. • 1 OS process for each Oracle
Background process
•1 OS process for each user
connection to the database
• In default implementation, with no
user connection, Total number of
Attached processes: 165
Conventional Method or Non - Threaded

7. With Threaded Execution enabled, Total number of Attached
processes reduced to 18.

9. V$Process

10. Online Optimizer Statistics
 Statistics are being gathered for objects created using
Direct Path operations like CTAS and Insert as select
operations.
 Only Basic Statistics are gathered
 Pre – 12c, Only Index creation had this feature.
 Will save Extra Full Table Scan(s) required to gather
statistics
 Useful in ETL Loads specifically for Staging table.
 Create Table AS (CTAS)
 Insert with Append (Bulk Load)
 Have its own restrictions as well..(Non-Empty
Segments,Tables with Virtual Columns….)

11. Contd… CTAS

12. Insert With Append

13. 10046 Trace

14. Statistics for GTT’s
• GTT shares its definition with system wide users
• Content in GTT is private to particular session.
• Pre 12c, statistics gathered on GTT’s were published system wide.
• In 12c, statistics on GTT’s can be kept private to the session collecting the stats.
• Useful in cases, where volume of data varies greatly across sessions.
• Controlled with GLOBAL_TEMP_TABLE_STATS preference of DBMS_STATS
• By default, preference is set to Session {SHARED}
• Its really useful in Solving Peoplesoft Temp Table Problem
SELECT
dbms_stats.get_prefs('GLOBAL_TEMP_TABLE_STATS','NUPNEJA','TEMP_GT')
FROM DUAL;

15. Temporary Undo
• By default, undo records for temporary tables are stored in the undo
tablespace and are logged in the redo.
• 12c introduces new concept of Temporary Undo: Undo generated by
transactions on temporary tables managed inside temporary undo
segments.
• Reduces amount of undo stored in undo tablespace.
• Inturn, reduces amount of redo generated.
• Managed using TEMP_UNDO_ENABLED parameter.
• Can be set at session level or system level.
• Default value is “FALSE”.
• Temp Undo statistics can be monitored through “V$TEMPUNDOSTAT”.

16. SQL> insert into temp_gt select * from dba_objects;
Default Behavior Temp Undo Enabled

17. Invisible Column
• Starting from 12c, one can add column to a table and make It as invisible.
• Can be used as low level security for a column.
• Different from system generated hidden columns
• Would not be shown up in result of select if not explicitly defined in Select
list of columns.
• Describe command will not show invisible column as part of table definition.
• “set colinvisible on” to see the hidden/invisible column
• Cannot create invisible column in
– External Tables
– Cluster Tables
– Temporary Tables

18. Multiple Indexes on same column
• Multiple Indexes on same column(s)
• Some characteristics of Index/Indexes
need to be different.
• Unique and non Unique
• B*Tree and Bitmap
• Partitioning Strategies like Local and Global.
• One of the Index needs to be Invisible.
• Useful for testing performance fixes.

19. Information Life Cycle Management (ILM)
• Conventional Techniques
– Storage Techniques : Moving data to Faster or
slower disks as per the usage of Data
– Database: Partitioning
• Oracle 12c
– Heat Map
• Data Compression
• Moving Data to Different Tablespace

20. DDL Logging
• In 12c, we can log the DDL statements running in a session or at system
level.
• Controlled by parameter “ENABLE_DDL_LOGGING”
• Can be set at Session level as well.
• DDL log is stored in the log/ddl subdirectory of the ADR home.
• DDL log contains one log record for each DDL statement issued by the
database/session.
• Two types of log files: XML and Text File.
• Can be useful to diagnose all the DDL’s running in a big package/program.
• Can be useful in troubleshooting any application program.

21. Contd.

22. Limit on PGA
• The Program Global Area (PGA) is a private memory region that contains
the data and control information for a server process.
• PGA_AGGREGATE_TARGET: Target aggregate PGA memory available to
all server processes attached to the instance.

23. PGA_AGGREGATE_LIMIT
• PGA_AGGREGATE_TARGET setting acts as a target, and not a
limit.
• PGA_AGGREGATE_LIMIT initialization parameter enables you to
specify a hard limit on PGA memory.
• Oracle Database aborts or terminates the sessions or processes
that are consuming the most untunable PGA memory
– Calls for sessions that are consuming the most untunable PGA memory are
aborted.
– If PGA memory usage is still over the PGA_AGGREGATE_LIMIT, then the
sessions and processes that are consuming the most untunable PGA memory
are terminated.

24. Excerpt from Trace

25. Moving Datafile Online
• Starting with Oracle 12c, we can move the datafile while it is online.
• ALTER DATABASE MOVE DATAFILE SQL statement to rename or
relocate online data files.
• Enables you to rename or relocate a data file while the database is open
and users are accessing the data file.
• If a file with the same name already exists in the destination location, the
existing file is not overwritten, and the statement returns an error.
• Keep option to retain the original file as well.
• Datafile must be online to perform this.
• You cannot move datafile of a pluggable database from container database.

26. Adaptive Query Optimization
•Enable Optimizer to make Run
– Time Adjustments to Execution
Plan
•Right Intent to have better
statistcis.
•Adaptive Plan
Join Methods
Parallel Distribution
•Adaptive Statistics
Dynamic Statistics
Automatic Re-optimization
SQL Plan Directives