Oracle 12c
New Features
Web Version
1
© 2013 - Julian Dyke
juliandyke.com
Agenda
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2
Introduction
Pluggable Database
Partial Indexes
Online Data File Move
Online Partition Move
Index Columns
Invisible Columns
Identity Clause
Session Sequences
Global Temporary Table Undo
Temporal Validity
Extended Columns
Row Limiting Clause
Histograms
Application Continuity
© 2013 - Julian Dyke
juliandyke.com
Introduction
This presentation investigates a selection of Oracle 12c new features that
I believe will be interesting to DBAs
The presentation was originally delivered at the UKOUG Conference 2013
in Manchester, England
I have added section headers containing comments and feedback from
delegates
3
© 2013 - Julian Dyke
juliandyke.com
What History Tells Us....

4
Oracle 9i , 10g and 11g
 R1 releases have been available for 18-24 months
 R2 releases have been available for several years
 R2 releases include terminal release
 Support has often been extended for terminal release

CPU and PSU support is limited for R1 releases
 Longer and more comprehensive for R2 releases

It is occasionally necessary to upgrade to a terminal release in order to
migrate to new functionality

In past releases there have been compatibility issues between new features
 Occasionally bugs....

Sometimes new features are documented but not released
© 2013 - Julian Dyke
juliandyke.com
New Features

Oracle Marketing concentrates on a limited subset of new features

5
Particularly new licensing options

Product Managers and Pre Sales are usually a better source of information

New features are often overlooked by everyone:

Particularly additional features in Standard/Enterprise Editions

Too many in each release to investigate them all

Documentation and support is often limited at initial release
© 2013 - Julian Dyke
juliandyke.com
Pluggable Database
Other presenters will have discussed pluggable databases in more detail
The concept was announced in September 2012 and I now believe it is
time to consider how and where it is appropriate to deploy pluggable
databases
My example of a possible deployment was a container database with a
large number of pluggable databases replacing SYBASE. I know that
SYBASE replacement has been a goal at a few of the larger banks for
many years.
Something I missed is that pluggable databases can be cloned allowing
test databases to be created rapidly from production databases.
I have not investigated this feature yet, so have limited my comments to
technical questions I would still like to answer
6
© 2013 - Julian Dyke
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Pluggable Database
7

Definitely the most attractive marketing feature
 Easy to explain
 Impresses managers and technical staff
 Obvious benefits

May be more efficient than virtualization for large numbers of similar
databases
 For example migrations from SYBASE

Potential reduction in resource consumption including:
 CPU
 memory
 background processes
 management costs
© 2013 - Julian Dyke
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Pluggable Database
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
Reduction in CPU might reduce processor license requirements

Separately licensed as Oracle Multi Tenant option
 US list price is $17,500 per processor (EE is $47,500)

All options will need to be licenced for all pluggable databases
 Possibly irrespective of usage e.g.
 Partitioning, Advanced Compression, Advanced Security
© 2013 - Julian Dyke
juliandyke.com
Pluggable Database
9

Only one redo thread per container instance
 Online redo logs may be a bottleneck

Data Guard
 Single configuration for container database
 Pluggable databases share redo thread
 May become difficult to manage if standby databases need to be rebuilt

Single large SGA may increase size of kernel page tables area for each
process (foreground / background or both)
 Will offset some of the savings in background process memory
 New In-Memory database may have same problem

Pluggable databases may contend for resources
 e.g. RAC background processes
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes
I believe this is one of the best features in Oracle 12c for sites using the
Partitioning Option
Most sites partition their tables based on time e.g. year, month, week, day
etc. Most activity centres around the latest (hot) partitions where indexes
are often required to optimize access paths. However, the cost of creating
an index for the entire table often prevents creation of appropriate
indexes as, in current versions, the index needs to be created for all
partitions, requiring additional storage and increasing backup and restore
times.
Partial indexes will not reduce redo generation, but could significantly
reduce overall database sizes as they will often affect the largest tables
I think the current implementation is limited, but I still think this is a great
feature
10
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes
11

One of the most important new features in Oracle 12.1

Allows additional indexes to be created for performance tuning

Potentially reduces amount of storage required for indexes
 May reduce backup and restore times
 Will probably not reduce redo / archive generation

Functionality is limited
 For a specific table, only one set of table partitions can be enabled for
index partitions
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes
12

Useful for range-based partitioned tables
 Create partial indexes on most recent (hot) partitions
 Alternatively create partial indexes on older (archived) partitions
 However cannot create partial indexes on both

Partial indexing must specified on table partitions
 INDEXING ON – partial indexes enabled
 INDEXING OFF – partial indexes disabled

If a table partition has INDEXING ON then all rows in that partition will be
indexed in each partial index
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes

Partial Local and Global Indexes
CREATE TABLE pcar
(
season_key
NUMBER,
race_key
NUMBER,
driver_key
VARCHAR2(4),
team_key
VARCHAR2(3),
position
NUMBER,
laps_completed NUMBER,
race_points
NUMBER
)
PARTITION BY RANGE (season_key)
(
PARTITION p2008 VALUES LESS THAN (2009) INDEXING OFF,
PARTITION p2009 VALUES LESS THAN (2010) INDEXING OFF,
PARTITION p2010 VALUES LESS THAN (2011) INDEXING OFF,
PARTITION p2011 VALUES LESS THAN (2012) INDEXING ON,
PARTITION p2012 VALUES LESS THAN (2013) INDEXING ON
);
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© 2013 - Julian Dyke
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Partial Indexes

Partial Local and Global Indexes
SELECT season_key, COUNT(*)
FROM pcar
GROUP BY season_key
ORDER BY season_key;
SEASON_KEY
2008
2009
2010
2011
2012
14
COUNT(*)
368
338
456
456
480
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes

Example - Partial Local Index
CREATE INDEX pcar1 ON pcar (driver_key) LOCAL
INDEXING PARTIAL;
dbms_stats.gather_index_stats
(
ownname => 'GP',
indname => 'PCAR1',
estimate_percent => NULL
);
SELECT partition_name,num_rows
FROM dba_ind_partitions
WHERE index_name = 'PCAR1';
PARTITION_NAME
P2008
P2009
P2010
P2011
P2012
15
NUM_ROWS
0
0
0
456
480
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes

Example - Partial Global Index
CREATE INDEX pcar2 ON pcar (team_key) GLOBAL
INDEXING PARTIAL;
dbms_stats.gather_index_stats
(
ownname => 'GP',
indname => 'PCAR2',
estimate_percent => NULL
);
SELECT num_rows
FROM dba_indexes
WHERE index_name = 'PCAR2';
NUM_ROWS
936
16
© 2013 - Julian Dyke
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Partial Indexes

Execution Plans - Partial Local Index
CREATE INDEX pcar3 ON pcar (season_key,race_key,position)
LOCAL INDEXING PARTIAL;
SELECT COUNT(*) FROM pcar
WHERE season_key = '2010';
0
1
2
3
-- Unindexed
SELECT STATEMENT
SORT AGGREGATE
PARTITION RANGE SINGLE
TABLE ACCESS FULL (PCAR)
Predicate Information (identified by operation id):
3 - filter("SEASON_KEY"=2010)

17
Cost = 14
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes

Execution Plans - Partial Local Index
CREATE INDEX pcar3 ON pcar (season_key,race_key,position)
LOCAL INDEXING PARTIAL;
SELECT COUNT(*) FROM pcar
WHERE season_key = '2011';
0
1
2
3
-- Indexed
SELECT STATEMENT
SORT AGGREGATE
PARTITION RANGE SINGLE
INDEX FAST FULL SCAN (PCAR3)
Predicate Information (identified by operation id):
3 - filter("SEASON_KEY"=2011)

18
Cost = 2
© 2013 - Julian Dyke
juliandyke.com
Partial Indexes

Execution Plans - Partial Local Index
CREATE INDEX pcar3 ON pcar (season_key,race_key,position)
LOCAL INDEXING PARTIAL;
SELECT COUNT(*) FROM pcar
WHERE season_key IN ('2010','2011');
0
1
2
3
-- Combined
SELECT STATEMENT
SORT AGGREGATE
PARTITION RANGE INLIST
TABLE ACCESS FULL (PCAR)
Predicate Information (identified by operation id):
3 - filter("SEASON_KEY"=2010 OR "SEASON_KEY"=2011)

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Cost = 27
© 2013 - Julian Dyke
juliandyke.com
Online Data File Move
This is a great new feature which I have already been using to resolve
space issues in my own virtual machines
I have successfully used this to move the data file containing the
SYSAUX tablespace – not sure I would want to risk it with the SYS
tablespace
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© 2013 - Julian Dyke
juliandyke.com
Online Data File Move

In Oracle 12.1 and above any data file can be moved online

For example:
ALTER DATABASE MOVE
DATAFILE '/u01/app/oradata/PROD/users01.dbf‘
TO '/u02/app/oradata/PROD/users01.dbf';
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
The database can be open and accessing the data file while the move is in
progress

Data files can be moved online:
 from file system to file system
 from file system to ASM
 from ASM to file system
 from ASM to ASM
© 2013 - Julian Dyke
juliandyke.com
Online Partition Move
This feature could be very useful for sites with partitioned tables on tiered
storage. Most likely usage is migrating partitions from fast expensive
storage (SSD) to slower cheaper storage (SAS or SATA)
The Oracle documentation hints that there are a lot of places where this
partition move can fail, and the DBMS_PART package contains some
subroutines that allow recovery from failures.
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© 2013 - Julian Dyke
juliandyke.com
Online Partition Move
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
In Oracle 12c partitions can be moved online

Useful for tiered storage
 Move from SSD to SAS to SATA

May be useful with OLTP compression

Also works for sub-partitions

Not supported in the following cases:
 For tables owned by SYS
 For IOTs
 For heap tables containing object types
 For heap tables containing bitmap join indexes or domain indexes
 If database-supplemental logging is enabled
 When parallel DML or direct path INSERTs are executing on the table
© 2013 - Julian Dyke
juliandyke.com
Online Partition Move

Consider the following example
CREATE TABLE pcar
(
season_key
NUMBER,
race_key
NUMBER,
driver_key
VARCHAR2(4),
team_key
VARCHAR2(3),
position
NUMBER,
laps_completed
NUMBER,
race_points
NUMBER
)
PARTITION BY RANGE (season_key)
(
PARTITION p2010 VALUES LESS THAN (2011) TABLESPACE sas,
PARTITION p2011 VALUES LESS THAN (2012) TABLESPACE sas,
PARTITION p2012 VALUES LESS THAN (2013) TABLESPACE ssd,
PARTITION p2013 VALUES LESS THAN (2014) TABLESPACE ssd
);
ALTER TABLE pcar MOVE PARTITION P2012 TABLESPACE sas;
24
© 2013 - Julian Dyke
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Online Partition Move

If online partition move operation fails, it can be cleaned up manually using:
 DBMS_PART.CLEANUP_ONLINE_OP

Clean up failed operations on <partition>
DBMS_PART.CLEANUP_ONLINE_OP (<schema>,<table>,<partition>);

Clean up failed operations on <table>
DBMS_PART.CLEANUP_ONLINE_OP (<schema>,<table>);

Clean up failed operations on <schema>
DBMS_PART.CLEANUP_ONLINE_OP (<schema>);

Clean up all failed operations in database
DBMS_PART.CLEANUP_ONLINE_OP;
25
© 2013 - Julian Dyke
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Index Columns
This is a useful new feature that allows multiple indexes to be created
with the same column list
For any given column list, only one index can be visible at a time.
However, this enhancement will allow new indexes to be created invisibly
and then made visible at an appropriate time.
26
© 2013 - Julian Dyke
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Index Columns

Multiple indexes can be created on the same set of columns

The following conditions must be met:

The indexes must have different properties e.g. type, partitioning,
uniqueness

Only one of the indexes can be VISIBLE at any given time
Recommendation: Check existing databases for indexes that
have been made invisible and then forgotten.
27
© 2013 - Julian Dyke
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Index Columns

Consider the following table and global index
CREATE TABLE pcar
(
season_key
NUMBER,
race_key
NUMBER,
driver_key
VARCHAR2(4),
team_key
VARCHAR2(3),
position
NUMBER,
laps_completed
NUMBER,
race_points
NUMBER
)
PARTITION BY RANGE (season_key)
(
PARTITION p2010 VALUES LESS THAN (2011),
PARTITION p2011 VALUES LESS THAN (2012),
PARTITION p2012 VALUES LESS THAN (2013),
PARTITION p2013 VALUES LESS THAN (2014)
);
CREATE INDEX pcar_global ON pcar (season_key,race_key,position);
28
© 2013 - Julian Dyke
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Index Columns

We realise the index should be local so we can drop partitions efficiently

The following statement fails with ORA-01408
CREATE INDEX pcar_local ON pcar (season_key,race_key,position) LOCAL;
*
ERROR at line 1:
ORA-01408: such column list already indexed

Create the new index INVISIBLE
CREATE INDEX pcar_local ON pcar (season_key,race_key,position) LOCAL
INVISIBLE;
Index created

*
Switch the indexes
ALTER INDEX pcar_global INVISIBLE;
ALTER INDEX pcar_local VISIBLE;

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The new index (PCAR_LOCAL) is now visible
 The old index (PCAR_GLOBAL) can be dropped
© 2013 - Julian Dyke
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Invisible Columns
I strongly believe this is a very dangerous feature. Whilst it achieves its
objectives, it is open to both accidental and malicious misuse as shown
in the example.
Misuse of this feature could introduce data corruptions that may go
unnoticed for months or years and prove to be extremely difficult to
resolve
30
© 2013 - Julian Dyke
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Invisible Columns

Consider the following table:
CREATE TABLE icar
(
season_key
race_key
driver_key
team_key
position
laps_completed
race_points
);
NUMBER,
NUMBER,
VARCHAR2(4),
VARCHAR2(3),
NUMBER,
NUMBER,
NUMBER
DESCRIBE icar
Name
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
LAPS_COMPLETED
RACE_POINTS
31
Null?
Type
NUMBER
NUMBER
VARCHAR2(4)
VARCHAR2(3)
NUMBER
NUMBER
NUMBER
© 2013 - Julian Dyke
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Invisible Columns

In the data dictionary COL$ contains the following rows for the ICAR table
SELECT c.name,c.type#,c.col#,c.intcol#,c.segcol#,
TO_CHAR (c.property,'XXXXXXXXXXXX') AS property
FROM sys.col$ c, sys.obj$ o, sys.user$ u
WHERE c.obj# = o.obj#
AND o.owner# = u.user#
AND u.name = 'GP‘
AND o.name = 'ICAR';
NAME
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
LAPS_COMPLETED
RACE_POINTS
32
TYPE#
2
2
1
1
2
2
2
COL# INTCOL# SEGCOL#
1
2
3
4
5
6
7
© 2013 - Julian Dyke
1
2
3
4
5
6
7
1
2
3
4
5
6
7
PROPERTY
0
0
0
0
0
0
0
juliandyke.com
Invisible Columns

Make the LAPS_COMPLETED column invisible:
ALTER TABLE icar MODIFY laps_completed INVISIBLE;

Describe the table again
DESCRIBE icar
Name
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
RACE_POINTS

33
Null?
Type
NUMBER
NUMBER
VARCHAR2(4)
VARCHAR2(3)
NUMBER
NUMBER
The LAPS_COMPLETED column is now invisible
© 2013 - Julian Dyke
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Invisible Columns

In the data dictionary COL$ now contains the following rows for ICAR:
SELECT c.name,c.type#,c.col#,c.intcol#,c.segcol#,
TO_CHAR (c.property,'XXXXXXXXXXXX') AS property
FROM sys.col$ c, sys.obj$ o, sys.user$ u
WHERE c.obj# = o.obj#
AND o.owner# = u.user#
AND u.name = 'GP‘
AND o.name = 'ICAR';
NAME
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
LAPS_COMPLETED
RACE_POINTS

34
TYPE#
2
2
1
1
2
2
2
COL# INTCOL# SEGCOL#
1
2
3
4
5
0
6
1
2
3
4
5
6
7
1
2
3
4
5
6
7
PROPERTY
0
0
0
0
0
400000020
0
0x400000000 = Invisible Column? 0x20 = Hidden Column
© 2013 - Julian Dyke
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Invisible Columns

Make the LAPS_COMPLETED column visible again:
ALTER TABLE icar MODIFY laps_completed VISIBLE;

Describe the table again:
DESCRIBE icar
Name
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
RACE_POINTS
LAPS_COMPLETED

35
Null?
Type
NUMBER
NUMBER
VARCHAR2(4)
VARCHAR2(3)
NUMBER
NUMBER
NUMBER
The LAPS_COMPLETED column now appears at end of table
© 2013 - Julian Dyke
juliandyke.com
Invisible Columns

In the data dictionary COL$ now contains the following rows for ICAR:
SELECT c.name,c.type#,c.col#,c.intcol#,c.segcol#,
TO_CHAR (c.property,'XXXXXXXXXXXX') AS property
FROM sys.col$ c, sys.obj$ o, sys.user$ u
WHERE c.obj# = o.obj#
AND o.owner# = u.user#
AND u.name = 'GP‘
AND o.name = 'ICAR';
NAME
SEASON_KEY
RACE_KEY
DRIVER_KEY
TEAM_KEY
POSITION
LAPS_COMPLETED
RACE_POINTS

36
TYPE#
COL# INTCOL# SEGCOL#
2
2
1
1
2
2
2
1
2
3
4
5
7
6
1
2
3
4
5
6
7
1
2
3
4
5
6
7
PROPERTY
0
0
0
0
0
0
0
LAPS_COMPLETED is now COL# 7
© 2013 - Julian Dyke
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Invisible Columns

Why is this dangerous? Consider the following:
INSERT INTO icar VALUES (2013,1,'KRAI','LOT',1,58,25);
SELECT * FROM icar;
SEASON_KEY
2013
RACE_KEY DRIVER_KEY TEAM_KEY
1
KRAI
POSITION
LAPS_COMPLETED
RACE_POINTS
1
58
25
LOT
ALTER TABLE icar MODIFY laps_completed INVISIBLE;
ALTER TABLE icar MODIFY laps_completed VISIBLE;
INSERT INTO icar VALUES (2013,1,'FALO','FER',2,58,18);
SELECT * FROM icar;
SEASON_KEY
2013
2013
37
RACE_KEY DRIVER_KEY TEAM_KEY
1
1
KRAI
FALO
POSITION
RACE_POINTS
LAPS_COMPLETED
1
2
25
58
58
18
LOT
FER
© 2013 - Julian Dyke
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Invisible Columns

Continued...
ALTER TABLE icar MODIFY race_points INVISIBLE;
ALTER TABLE icar MODIFY race_points VISIBLE;
INSERT INTO icar VALUES (2013,1,‘SVET',‘RBR',3,58,15);
SELECT * FROM icar;
SEASON_KEY
2013
2013
2013

38
RACE_KEY DRIVER_KEY TEAM_KEY
1
1
1
KRAI
FALO
SVET
POSITION
LAPS_COMPLETED
RACE_POINTS
1
2
3
58
18
58
25
58
15
LOT
FER
RBR
Column order is restored, but Fernando Alonso now has 58 points
© 2013 - Julian Dyke
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Identity Clause
This new feature simplifies management of sequences used as primary
keys for tables. The identity clause allows an implicit index to be created
for the specified column.
If the table is truncated, the sequence is unaffected
If the table is dropped and recreated the sequence will dropped and
recreated and will restart at the minimum value for the next insertion
39
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Identity Clause

In Oracle 12.1 and above an identity clause can be used to specify a sequence
column in CREATE TABLE and ALTER TABLE statements

Syntax is:
GENERATED
[ ALWAYS | BY DEFAULT [ ON NULL ] ]
AS IDENTITY [ ( identity_options ) ]

where <identity_options> are:
{ START WITH ( integer | LIMIT VALUE )
| INCREMENT BY integer
| ( MAXVALUE integer | NOMAXVALUE )
| ( MINVALUE integer | NOMINVALUE )
| ( CYCLE | NOCYCLE )
| ( CACHE integer | NOCACHE )
| ( ORDER | NOORDER ) } . . .
40
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Identity Clause

Example:
CREATE TABLE driver2
(
driver_key NUMBER GENERATED AS IDENTITY,
driver_name VARCHAR2(30),
driver_dob DATE,
country_key VARCHAR2(3)
);
INSERT INTO driver2 (driver_name,driver_dob,country_key)
VALUES ('Sebastian Vettel','03-JUL-1987','GER');
INSERT INTO driver2 (driver_name,driver_dob,country_key)
VALUES ('Fernando Alonso',‘29-JUL-1981','SPA');
INSERT INTO driver2 (driver_name,driver_dob,country_key)
VALUES ('Kimi Raikkonen','17-OCT-1979','FIN');
SELECT * FROM driver2;
DRIVER_KEY
1
2
3
41
DRIVER_NAME DRIVER_DOB
Sebastian Vettel 03-JUL-1987
Fernando Alonso 29-JUL-1981
Kimi Raikkonen 17-OCT-1979
© 2013 - Julian Dyke
COUNTRY_KEY
GER
SPA
FIN
juliandyke.com
Identity Clause

DESCRIBE includes identity column
DESCRIBE driver2

42
Name
Null?
Type
DRIVER_KEY
DRIVER_NAME
DRIVER_DOB
COUNTRY_KEY
NOT NULL
NUMBER
VARCHAR2(30)
DATE
VARCHAR2(3)
No additional indexes are created
© 2013 - Julian Dyke
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Identity Clause

Columns are stored in the data dictionary as follows:
SELECT c.name,c.type#,c.col#,c.intcol#,c.segcol#,
TO_CHAR (c.property,'XXXXXXXXXX') AS property
FROM sys.col$ c, sys.obj$ o, sys.user$ u
WHERE c.obj# = o.obj#
AND o.owner# = u.user#
AND u.name = 'GP‘
AND o.name = 'DRIVER2‘
ORDER BY intcol#;
NAME
TYPE#
DRIVER_KEY
DRIVER_NAME
DRIVER_DOB
COUNTRY_KEY


43
2
1
12
1
COL#
INTCOL#
SEGCOL#
PROPERTY
1
2
3
4
1
2
3
4
1
2
3
4
2800000000
0
0
0
0x800000000 = Default as Sequence
0x2000000000 = Generated ALWAYS identity column
© 2013 - Julian Dyke
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Identity Clause

Default value for DRIVER_KEY column can be found in DBA_TAB_COLUMNS:
SELECT data_default
FROM dba_tab_columns
WHERE owner = 'GP‘
AND table_name = 'DRIVER2‘
AND column_name = 'DRIVER_KEY';
"GP"."ISEQ$$_92584".nextval

In this example 92584 is the object ID of the GP.DRIVER2 table
SELECT
sequence_owner AS owner,min_value,max_value,increment_by,
cycle_flag,order_flag,cache_size
FROM dba_sequences
WHERE sequence_name = 'ISEQ$$_92584';
OWNER
GP
44
MIN_VALUE
1
MAX_VALUE
INCREMENT_BY
1.0000E+28
1
© 2013 - Julian Dyke
C O CACHE_SIZE
N
N
20
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Session Sequences
This new feature allows sequences to be created that exist for the lifetime
of the current session only.
Intended for use with global temporary tables, but possibly useful in
other places and more flexible than the ROWNUM pseudo column
45
© 2013 - Julian Dyke
juliandyke.com
Session Sequences

In Oracle 12.1 and above sequences can have session visibility
 Current value only visible to session

For example:
CREATE SEQUENCE seq1 SESSION;
SQL> CONNECT gp/gp
SQL> SELECT seq1.NEXTVAL FROM dual;
NEXTVAL
1
SQL> SELECT seq1.NEXTVAL FROM dual;
NEXTVAL
2
SQL> CONNECT gp/gp
SQL> SELECT seq1.NEXTVAL FROM dual;
NEXTVAL
1
46
© 2013 - Julian Dyke
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Global Temporary
Table Undo
This new feature allows undo for global temporary tables to be written to
the temporary table space
It will not have much impact for insertions, but could have a significant
impact on redo generation caused by GTT undo during updates
I envisage this becoming the default in future versions
47
© 2013 - Julian Dyke
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Global Temporary Table Undo
48

By default DML on Global Temporary Tables
 Does not generate redo directly
 Does generate undo and indirect redo

Undo is required to rollback transactions

Redo will be archived, backed up , propagated to standby etc

In Oracle 12c Global Temporary Table undo can be stored in a temporary
tablespace
 Set TEMP_UNDO_ENABLED = TRUE

Will not have much impact for INSERT statements
 May have significant impact for UPDATE and DELETE statements
 Review whether DELETE statements are necessary
© 2013 - Julian Dyke
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Temporal Validity
Temporal validity allows tables to be created where rows are valid for a
specific period of time
A major defect is that is not possible to create primary keys with temporal
validity. This functionality may be added in a future release, until which
time this feature may be of limited use.
49
© 2013 - Julian Dyke
juliandyke.com
Temporal Validity
50

Flashback Data Archive was introduced in Oracle 11.1
 Originally known as Total Recall

Allows historic data to be inspected at any point in time

Was a separately licensed option
 Consequently not very popular

Now available free in Enterprise Edition (at least)
 Including Oracle 11.2

In Oracle 12.1 and above Temporal Validity builds on these concepts
© 2013 - Julian Dyke
juliandyke.com
Temporal Validity

For example:
CREATE TABLE driver
(
driver_key
VARCHAR2(4),
team_key
VARCHAR2(3),
joining_date DATE,
leaving_date DATE,
PERIOD FOR team_member_valid_time (joining_date,leaving_date)
);

Insert some data
INSERT INTO driver VALUES ('FALO','FER','01-JAN-2010',NULL);
INSERT INTO driver VALUES ('FMAS','FER','01-JAN-2006','31-DEC-2013');
INSERT INTO driver VALUES ('KRAI','FER','01-JAN-2007','31-DEC-2009');
INSERT INTO driver VALUES ('RBAR','FER','01-JAN-2000','31-DEC-2007');
INSERT INTO driver VALUES ('MSCH','FER','01-JAN-1996','31-DEC-2006');

51
Note: the above data is inaccurate
© 2013 - Julian Dyke
juliandyke.com
Temporal Validity

For example:
SELECT * FROM driver;
DRIVER_KEY
FALO
FMAS
KRAI
RBAR
MSCH

TEAM_KEY
FER
FER
FER
FER
FER
JOINING_DATE
01-JAN-2010
01-JAN-2006
01-JAN-2007
01-JAN-2000
01-JAN-1996
LEAVING_DATE
31-DEC-2013
31-DEC-2009
31-DEC-2007
31-DEC-2006
Who was in the team for the 2009 British Grand Prix qualifying?
SELECT * FROM driver
AS OF PERIOD FOR team_member_valid_time TO_DATE (‘20-JUN-2009’);
DRIVER_KEY
FMAS
KRAI
52
TEAM_KEY
FER
FER
JOINING_DATE
01-JAN-2006
01-JAN-2007
© 2013 - Julian Dyke
LEAVING_DATE
31-DEC-2013
31-DEC-2009
juliandyke.com
Temporal Validity

Describe the driver table
DESCRIBE driver
Name
DRIVER_KEY
TEAM_KEY
JOINING_DATE
LEAVING_DATE
53
Null?
Type
VARCHAR2(4)
VARCHAR2(3)
DATE
DATE
© 2013 - Julian Dyke
juliandyke.com
Temporal Validity

List the columns in COL$
SELECT c.name,c.col#,c.intcol#,c.segcol#,c.type#,TO_CHAR (c.property,'XXXXX')
FROM sys.col$ c, sys.obj$ o
WHERE c.obj# = o.obj#
AND o.name = 'DRIVER3‘
ORDER BY c.intcol#
NAME
COL# INTCOL# SEGCOL#
TEAM_MEMBER_VALID_TIME
0
1
0
DRIVER_KEY
1
2
1
TEAM_KEY
2
3
2
JOINING_DATE
3
4
3
LEAVING_DATE
4
5
4



54
TYPE#
2
1
1
12
12
PROPERTY
10028
0
0
0
0
0x10000 = Virtual Column
0x20 = Hidden Column
0x8 = Virtual Column
© 2013 - Julian Dyke
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Extended Columns
This feature allows the size of VARCHAR2, NVARCHAR2 and RAW
columns stored in the database to be increased to 32767 bytes. If the
value is longer than 4000 bytes it is stored as an out of line LOB
Built-in functions appear to work correctly with the longer column sizes
This feature needs to be enabled by setting MAX_STRING_SIZE to
EXTENDED. This parameter is not set by default. You may want to set this
parameter before creating a database, otherwise you will need an outage
as the parameter must be set when the database is in UPGRADE mode
55
© 2013 - Julian Dyke
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Extended Columns

In Oracle 12c and above maximum column length has increased
Data Type
56
Oracle 11.2
and below
Oracle 12.1
and above
VARCHAR2
4000
32767
NVARCHAR2
2000
16383
RAW
2000
32767

Note that NVARCHAR2 limits assume two bytes per character

Maximum length of CHAR and NCHAR remains at 2000 and 1000 respectively

Extended columns are stored as SECUREFILE LOBs
 Stored in line if <= 4K
 Stored out of line if > 4K

COMPATIBLE parameter must be 12.0.0.0.0 or above
© 2013 - Julian Dyke
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Extended Columns

By default attempts to create an extended column will fail:
ALTER TABLE car MODIFY notes VARCHAR2(32767);
*
ERROR at line 1:
ORA-00910: specified length too long for its datatype

MAX_STRING_SIZE parameter must be set to EXTENDED
 Default is value is STANDARD

MAX_STRING_SIZE parameter cannot be updated when database is open:
ALTER SYSTEM SET max_string_size = 'EXTENDED'
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is
invalid
ORA-14694: database must in UPGRADE mode to begin
MAX_STRING_SIZE migration
57
© 2013 - Julian Dyke
juliandyke.com
Extended Columns

To change the MAX_STRING_SIZE parameter, restart the database in
UPGRADE mode
SQL> SHUTDOWN IMMEDIATE
SQL> STARTUP MIGRATE

Set the parameter value to EXTENDED:
SQL> ALTER SYSTEM SET max_string_size = EXTENDED;

Run the utl32k.sql script
SQL> @$ORACLE_HOME/rdbms/admin/utl32k.sql;

Restart the database
SQL> SHUTDOWN IMMEDIATE
SQL> STARTUP

58
It is not possible to convert the MAX_STRING_SIZE parameter back from
EXTENDED to STANDARD
© 2013 - Julian Dyke
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Extended Columns

When MAX_STRING_SIZE is set to EXTENDED then tables can be created with
extended columns:
CREATE TABLE ecar
(
season_key
race_key
driver_key
team_key
position
laps_completed
notes
race_points
);

NUMBER,
NUMBER,
VARCHAR2(4),
VARCHAR2(3),
NUMBER,
NUMBER,
VARCHAR2(32767),
NUMBER
Alternatively maximum size of columns in existing tables can be increased:
ALTER TABLE car MODIFY notes VARCHAR2(32767);
59
© 2013 - Julian Dyke
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Extended Columns

Extended columns are implemented as SECUREFILE LOBs
SELECT column_name,segment_name,securefile
FROM dba_lobs
WHERE owner = 'GP‘
AND table_name = 'ECAR';

COLUMN_NAME
SEGMENT_NAME
SECUREFILE
NOTES
SYS_LOB0000092626C00007$$
YES
SECUREFILE LOBs have a system-created index
SELECT column_name,index_name
FROM dba_lobs
WHERE owner = 'GP‘
AND table_name = 'ECAR';
60
COLUMN_NAME
INDEX_NAME
NOTES
SYS_IL0000092626C00007$$
© 2013 - Julian Dyke
juliandyke.com
Row Limiting Clause
This feature provides a more comprehensive syntax for Top-N queries
The new syntax uses analytic query operations as opposed to regular
sort options
It is probably worth doing comparative performance tests before adopting
the new syntax
Beware with the OFFSET clause – each invocation will require a full sort
of the data before returning any rows
61
© 2013 - Julian Dyke
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Row Limiting Clause

In Oracle 12c and above SELECT statements can include the FETCH FIRST
clause
 Limits rows returned by query
 Optional replacement syntax for TOP-N queries

Syntax is:
[ OFFSET offset { ROW | ROWS } ]
[ FETCH { FIRST | NEXT } [ { rowcount | percent PERCENT } ]
{ ROW | ROWS } { ONLY | WITH TIES } ]
62

OFFSET specifies number of rows to skip before row limiting begins

FETCH specifies number of rows or percentage of rows to return
 ONLY return exactly the number of rows specified
 WITH TIES return additional rows with same sort key as last row fetched
© 2013 - Julian Dyke
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Row Limiting Clause
63

An ORDER BY clause is normally required to ensure that sort order is
deterministic

Restrictions
 Cannot be specified in SELECT FOR UPDATE statements
 Cannot be used with CURRVAL or NEXTVAL pseudo-columns
 Cannot be used with materialized view incremental refresh
© 2013 - Julian Dyke
juliandyke.com
Row Limiting Clause

Example – top ten drivers in 2012
Driver Name
Sebastian Vettel
Fernando Alonso
Kimi Raikkonen
Lewis Hamilton
Jenson Button
Mark Webber
Felipe Massa
Romain Grosjean
Nico Rosberg
Sergio Perez
64
© 2013 - Julian Dyke
Points
281
278
207
190
188
179
122
96
93
66
juliandyke.com
Row Limiting Clause

Example – Top N query
SELECT * FROM
(
SELECT d.driver_name,t.team_name,SUM(c.driver_points)
FROM car c,driver d,team t
WHERE c.season_key = 2012
AND c.driver_key = d.driver_key
AND c.team_key = t.team_key
GROUP BY d.driver_name,t.team_name
ORDER BY SUM(c.driver_points) DESC
)
WHERE ROWNUM <= 5;
Driver Name
Sebastian Vettel
Fernando Alonso
Kimi Raikkonen
Lewis Hamilton
Jenson Button
Points
281
278
207
190
188
----------------------------------------------------------------------| Id | Operation
| Name
| Rows | Bytes | Cost (%CPU)|
----------------------------------------------------------------------|
0 | SELECT STATEMENT
|
|
5 |
335 |
41
(0)|
|* 1 | COUNT STOPKEY
|
|
|
|
|
|
2 |
VIEW
|
|
480 | 32160 |
41
(0)|
|* 3 |
SORT ORDER BY STOPKEY|
|
480 | 23520 |
41
(0)|
|
4 |
HASH GROUP BY
|
|
480 | 23520 |
41
(0)|
|* 5 |
HASH JOIN
|
|
480 | 23520 |
41
(0)|
|
6 |
TABLE ACCESS FULL | TEAM
|
104 | 1248 |
2
(0)|
|* 7 |
HASH JOIN
|
|
480 | 17760 |
39
(0)|
|* 8 |
TABLE ACCESS FULL| CAR
|
480 | 8160 |
36
(0)|
|
9 |
TABLE ACCESS FULL| DRIVER |
493 | 9860 |
3
(0)|
-----------------------------------------------------------------------
65
© 2013 - Julian Dyke
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Row Limiting Clause

Example – Fetch Only Clause
SELECT d.driver_name,t.team_name,SUM(c.driver_points)
FROM car c,driver d,team t
WHERE c.season_key = 2012
AND c.driver_key = d.driver_key
AND c.team_key = t.team_key
GROUP BY d.driver_name,t.team_name
ORDER BY SUM(c.driver_points) DESC
FETCH FIRST 5 ROWS ONLY;
Driver Name
Sebastian Vettel
Fernando Alonso
Kimi Raikkonen
Lewis Hamilton
Jenson Button
Points
281
278
207
190
188
------------------------------------------------------------------------| Id | Operation
| Name
| Rows | Bytes | Cost (%CPU)|
------------------------------------------------------------------------|
0 | SELECT STATEMENT
|
|
480 | 44640 |
41
(0)|
|
1 | SORT ORDER BY
|
|
480 | 44640 |
41
(0)|
|* 2 |
VIEW
|
|
480 | 44640 |
41
(0)|
|* 3 |
WINDOW SORT PUSHED RANK|
|
480 | 23520 |
41
(0)|
|
4 |
HASH GROUP BY
|
|
480 | 23520 |
41
(0)|
|* 5 |
HASH JOIN
|
|
480 | 23520 |
41
(0)|
|
6 |
TABLE ACCESS FULL
| TEAM
|
104 | 1248 |
2
(0)|
|* 7 |
HASH JOIN
|
|
480 | 17760 |
39
(0)|
|* 8 |
TABLE ACCESS FULL | CAR
|
480 | 8160 |
36
(0)|
|
9 |
TABLE ACCESS FULL | DRIVER |
493 | 9860 |
3
(0)|
-------------------------------------------------------------------------
66
© 2013 - Julian Dyke
juliandyke.com
Row Limiting Clause

Example – Fetch Percent With Ties Clause
SELECT d.driver_name,t.team_name,SUM(c.driver_points)
FROM car c,driver d,team t
WHERE c.season_key = 2012
AND c.driver_key = d.driver_key
AND c.team_key = t.team_key
GROUP BY d.driver_name,t.team_name
ORDER BY SUM(c.driver_points) DESC
FETCH FIRST 20 PERCENT ROWS WITH TIES;
Driver Name
Points
Sebastian Vettel
Fernando Alonso
Kimi Raikkonen
Lewis Hamilton
Jenson Button
281
278
207
190
188
----------------------------------------------------------------------| Id | Operation
| Name
| Rows | Bytes | Cost (%CPU)|
----------------------------------------------------------------------|
0 | SELECT STATEMENT
|
|
480 | 50880 |
41
(0)|
|
1 | SORT ORDER BY
|
|
480 | 50880 |
41
(0)|
|* 2 |
VIEW
|
|
480 | 50880 |
41
(0)|
|
3 |
WINDOW SORT
|
|
480 | 23520 |
41
(0)|
|
4 |
HASH GROUP BY
|
|
480 | 23520 |
41
(0)|
|* 5 |
HASH JOIN
|
|
480 | 23520 |
41
(0)|
|
6 |
TABLE ACCESS FULL | TEAM
|
104 | 1248 |
2
(0)|
|* 7 |
HASH JOIN
|
|
480 | 17760 |
39
(0)|
|* 8 |
TABLE ACCESS FULL| CAR
|
480 | 8160 |
36
(0)|
|
9 |
TABLE ACCESS FULL| DRIVER |
493 | 9860 |
3
(0)|
-----------------------------------------------------------------------
67
© 2013 - Julian Dyke
juliandyke.com
Row Limiting Clause

Example – Fetch with Offset Clause
SELECT d.driver_name,t.team_name,SUM(c.driver_points)
FROM car c,driver d,team t
WHERE c.season_key = 2012
AND c.driver_key = d.driver_key
AND c.team_key = t.team_key
GROUP BY d.driver_name,t.team_name
ORDER BY SUM(c.driver_points) DESC
OFFSET 5 ROWS
FETCH FIRST 5 ROWS ONLY;
Driver Name
Mark Webber
Felipe Massa
Romain Grosjean
Nico Rosberg
Sergio Perez
Points
179
122
96
93
66
------------------------------------------------------------------------| Id | Operation
| Name
| Rows | Bytes | Cost (%CPU)|
------------------------------------------------------------------------|
0 | SELECT STATEMENT
|
|
480 | 44640 |
41
(0)|
|
1 | SORT ORDER BY
|
|
480 | 44640 |
41
(0)|
|* 2 |
VIEW
|
|
480 | 44640 |
41
(0)|
|* 3 |
WINDOW SORT PUSHED RANK|
|
480 | 23520 |
41
(0)|
|
4 |
HASH GROUP BY
|
|
480 | 23520 |
41
(0)|
|* 5 |
HASH JOIN
|
|
480 | 23520 |
41
(0)|
|
6 |
TABLE ACCESS FULL
| TEAM
|
104 | 1248 |
2
(0)|
|* 7 |
HASH JOIN
|
|
480 | 17760 |
39
(0)|
|* 8 |
TABLE ACCESS FULL | CAR
|
480 | 8160 |
36
(0)|
|
9 |
TABLE ACCESS FULL | DRIVER |
493 | 9860 |
3
(0)|
-------------------------------------------------------------------------
68
© 2013 - Julian Dyke
juliandyke.com
Histograms
There are several enhancements to histograms in Oracle 12c. This
section concentrates on the increase in maximum number of buckets
from 254 to 2048. Increasing the number of buckets allows better
cardinalities to be estimated by the optimization, potentially generating
more efficient execution plans
The increased bucket sizes work for both single column and multi column
statistics
This is particular useful with my Formula 1 database which (for the period
1961 to 2012) contains 492 drivers and 1289 driver/team combinations.
69
© 2013 - Julian Dyke
juliandyke.com
Histograms

Maximum bucket size increased to 2048

Default bucket size is still 256

For example, an inefficient execution plan has been generated for a query
 We determine that the root cause is poor cardinality estimates for the
DRIVER_KEY column in the CAR table

The DRIVER_KEY column has 492 distinct values
SELECT COUNT (DISTINCT (driver_key)) AS driver_key FROM car;
DRIVER_KEY
492
70
© 2013 - Julian Dyke
juliandyke.com
Histograms

Default statistics collection only gathers minimum and maximum values:
dbms_stats.gather_table_stats
(
ownname => 'GP',
tabname => 'CAR',
estimate_percent => NULL
);
SELECT COUNT (*) FROM dba_histograms
WHERE owner = ‘GP’
AND table_name = ‘CAR’
AND column_name = ‘DRIVER_KEY’;
COUNT (*)
2
71
© 2013 - Julian Dyke
juliandyke.com
Histograms

Collect histograms on the DRIVER_KEY column
dbms_stats.gather_table_stats
(
ownname => 'GP',
tabname => 'CAR',
estimate_percent => NULL
method_opt => 'FOR COLUMNS driver_key'
);
SELECT COUNT (*) FROM dba_histograms
WHERE owner = ‘GP’
AND table_name = ‘CAR’
AND column_name = ‘DRIVER_KEY’;
COUNT (*)
75

72
Default behaviour is to create a maximum of 256 buckets
© 2013 - Julian Dyke
juliandyke.com
Histograms

If more than 256 buckets are required, this must be specified explicitly:
dbms_stats.gather_table_stats
(
ownname => 'GP',
tabname => 'CAR',
estimate_percent => NULL
method_opt => 'FOR COLUMNS driver_key SIZE 2048'
);
SELECT COUNT (*) FROM dba_histograms
WHERE owner = ‘GP’
AND table_name = ‘CAR’
AND column_name = ‘DRIVER_KEY’;
COUNT (*)
492
73
© 2013 - Julian Dyke
juliandyke.com
Histograms

Multi-Column Statistics
DECLARE
l_extension_name VARCHAR2(30);
BEGIN
l_extension_name := dbms_stats.create_extended_stats
(
ownname => 'GP',
tabname => 'CAR6',
extension => '(driver_key,team_key)‘
);
END;
BEGIN
dbms_stats.gather_table_stats
(
ownname => 'GP',
tabname => 'CAR6',
estimate_percent => NULL,
method_opt => 'FOR COLUMNS (DRIVER_KEY,TEAM_KEY) SIZE 2048‘
);
END;
74
© 2013 - Julian Dyke
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Histograms

Multi-Column Statistics
DECLARE
l_extension_name VARCHAR2(30);
BEGIN
l_extension_name := dbms_stats.create_extended_stats
(
ownname => 'GP',
tabname => 'CAR6',
extension => '(driver_key,team_key)‘
);
END;
BEGIN
dbms_stats.gather_table_stats
(
ownname => 'GP',
tabname => 'CAR6',
estimate_percent => NULL,
method_opt => 'FOR COLUMNS (DRIVER_KEY,TEAM_KEY) SIZE 2048‘
);
END;
75
© 2013 - Julian Dyke
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Histograms

Multi-Column Statistics
SELECT COUNT(*) FROM gp.car
WHERE driver_key = ‘MSCH'
AND team_key = 'FER';
COUNT(*)
181
Id
Operation
0
1
2
Rows
Bytes
SELECT STATEMENT
1
9
SORT AGGREGATE
1
9
181
1629
TABLE ACCESS FULL
Name
CAR
Cost (%CPU)
Time
39
(0)
00:00:01
39
(0)
00:00:01
Correct
Cardinality
776
© 2013 - Julian Dyke
juliandyke.com
Histograms

Multi-Column Statistics
SELECT COUNT(*) FROM gp.car
WHERE driver_key = ‘MSCH'
AND team_key = ‘JOR';
COUNT(*)
1
Id
Operation
0
1
2
Rows
Bytes
SELECT STATEMENT
1
9
SORT AGGREGATE
1
9
1
1629
TABLE ACCESS FULL
Name
CAR
Cost (%CPU)
Time
39
(0)
00:00:01
39
(0)
00:00:01
Correct
Cardinality
777
© 2013 - Julian Dyke
juliandyke.com
Application Continuity
This is potentially a very important new feature which allows
uncommitted transactions to be replayed in another instance following a
RAC or Data Guard failover or session relocation
I anticipate many sites will wish to take advantage of this new
functionality.
Initially I have attempted to create a simple test example of this
functionality using a JDBC thin client application, but have so far been
unsuccessful.
I know that Trivadis have successful created a demonstration of
Application Continuity using the Universal Connection Pool (UCP) so it
does work.
Further investigation is required for the JDBC Thin example. In the
meantime this session contains the configuration that I have completed
so far.
78
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Application Continuity
79

Failed transactions are replayed on another instance / database
 Similar goals to TAF and FCF
 Better implementation

Can be configured for:
 RAC
 Data Guard
 Single Instance

Must use one of:
 Weblogic pool
 Universal Connection Pool (UCP)
 JDBC Thin

OCI not currently supported

Limitations may drive future development decisions e.g. connections pools
© 2013 - Julian Dyke
juliandyke.com
Application Continuity
80

JDBC calls should handle events for the current session such as:
 Service shutdown
 Instance failure
 Network failure
 Node failure

Session will attempt to reconnect again (same or different instance)
 Failed transactions will be rolled back and re-executed

Similar (but not the same) as Database Replay
 Calls replayed with bind variables etc.
 Fewer synchronization issues – replay only includes last uncommitted
transaction
© 2013 - Julian Dyke
juliandyke.com
Application Continuity


Must connect to a user-defined service
 Not the database service
E.g. for single instance database
DECLARE
l_arr DBMS_SERVICE.SVC_PARAMETER_ARRAY;
BEGIN
l_arr ('FAILOVER_TYPE')
:= 'TRANSACTION';
l_arr ('REPLAY_INITIATION_TIMEOUT')
:= 600;
l_arr ('FAILOVER_DELAY')
:= 3;
l_arr ('FAILOVER_RETRIES')
:= 20;
l_arr ('SESSION_STATE_CONSISTENCY') := 'DYNAMIC';
l_arr ('COMMIT_OUTCOME')
:= 'TRUE';
l_arr ('AQ_HA_NOTIFICATIONS')
:= 'TRUE';
DBMS_SERVICE.CREATE_SERVICE
(
service_name => 'SERVICE1',
network_name => 'SERVICE1‘,
parameter_array => l_arr
);
END;
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Application Continuity

E.g. for a RAC database
srvctl add service -db TEST \
-service SERVICE1 \
-preferred TEST1 \
-available TEST2 \
-failovertype TRANSACTION \
-notification TRUE \
-commit_outcome TRUE \
-replay_init_time 600 \
-failoverretry 30 \
-failoverdelay 10

Remember to start the service...
srvctl start service –d TEST –s SERVICE1 –i TEST1
82
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Application Continuity

Client connection string should include values for:
 TRANSPORT_CONNECT_TIMEOUT
 CONNECT_TIMEOUT
 RETRY_COUNT

For example:
jdbc:oracle:thin:gp/gp@(DESCRIPTION=(TRANSPORT_CONNECT_TIMEOUT=3)
(CONNECT_TIMEOUT=60)(RETRY_COUNT=10)(FAILOVER=ON)
(ADDRESS=(PROTOCOL=tcp)(PORT=1521)(HOST=vmcluster1-scan.juliandyke.com))
(CONNECT_DATA=(SERVICE_NAME=SERVICE1)))

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REMOTE_LISTENER database parameter must include
 SCAN name if clients specify SCAN names
 Node names if clients specify address list
© 2013 - Julian Dyke
juliandyke.com
Application Continuity

Configure the Oracle JDBC 12c Replay Data Source in the property file or in
the thin JDBC application e.g.
import oracle.jdbc.replay.OracleDataSourceImpl;
import oracle.jdbc.replay.ReplayableConnection;
OracleDataSourceImpl ods = new OracleDataSourceImpl();
ods.setURL(url);
connection = ods.getConnection();
connection.setAutoCommit (false);
...
((ReplayableConnection)connection).beginRequest();
# Application processing
((ReplayableConnection)connection).endRequest();

84
Requires $ORACLE_HOME/jdbc/lib/ojdbc6.jar on CLASSPATH
© 2013 - Julian Dyke
juliandyke.com
Application Continuity

Debugging replayable connections

Add $ORACLE_HOME/jdbc/lib/ojdbc6_g.jar to the CLASSPATH

Add the following to the properties file
oracle.jdbc.internal.replay.level = FINEST
handlers = java.util.logging.FileHandler
java.util.logging.FileHandler.pattern = /home/oracle/12c/appcon2/replay_%U.trc
java.util.logging.FileHandler.limit = 500000000
java.util.logging.FileHandler.count = 1000
java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

Execute using:
java -Djava.util.logging.config.file=/home/oracle/appcon/properties J7

85
Writes trace to replay_0.trc.0
© 2013 - Julian Dyke
juliandyke.com
Application Continuity
86

Potentially a very powerful feature
 Easier to implement, test and support than TAF
 Builds on FCF

Applications need to be designed specifically for application continuity
 Very difficult to retrofit existing applications
 Special attention required for pseudo columns such as SYSDATE
 Sequences should use the new KEEP clause

If you plan to use this feature in the future, I recommend
 DBAs become familiar with it in Oracle 12.1 so they can support
developments
 New applications follow the development guidelines for this feature
 Expect to deploy the new applications in Oracle 12.2
© 2013 - Julian Dyke
juliandyke.com
Thank You For Your Interest
info@juliandyke.com
87
© 2013 - Julian Dyke
juliandyke.com