Juliandyke.com 1 © 2013 - Julian Dyke Web Version Oracle 12c New Features.

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1 © 2013 - Julian Dyke

Web Version

Oracle 12cNew Features

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Agenda

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

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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

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What History Tells Us.... 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

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New Features Oracle Marketing concentrates on a limited subset of new features

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

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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

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Pluggable Database 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

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Pluggable Database 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

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Pluggable Database 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

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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

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Partial Indexes 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

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Partial Indexes 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

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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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Partial Indexes Partial Local and Global Indexes

SELECT season_key, COUNT(*)FROM pcarGROUP BY season_keyORDER BY season_key;

SEASON_KEY COUNT(*)2008 3682009 3382010 4562011 4562012 480

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Partial Indexes Example - Partial Local Index

CREATE INDEX pcar1 ON pcar (driver_key) LOCALINDEXING PARTIAL;

dbms_stats.gather_index_stats(

ownname => 'GP',indname => 'PCAR1',estimate_percent => NULL

);

SELECT partition_name,num_rowsFROM dba_ind_partitionsWHERE index_name = 'PCAR1';

PARTITION_NAME NUM_ROWSP2008 0P2009 0P2010 0P2011 456P2012 480

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Partial Indexes Example - Partial Global Index

CREATE INDEX pcar2 ON pcar (team_key) GLOBALINDEXING PARTIAL;

dbms_stats.gather_index_stats(

ownname => 'GP',indname => 'PCAR2',estimate_percent => NULL

);

SELECT num_rowsFROM dba_indexesWHERE index_name = 'PCAR2';

NUM_ROWS936

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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 pcarWHERE season_key = '2010'; -- Unindexed

0 SELECT STATEMENT1 SORT AGGREGATE2 PARTITION RANGE SINGLE3 TABLE ACCESS FULL (PCAR)

Predicate Information (identified by operation id):

3 - filter("SEASON_KEY"=2010)

Cost = 14

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SELECT COUNT(*) FROM pcarWHERE season_key = '2011'; -- Indexed

0 SELECT STATEMENT1 SORT AGGREGATE2 PARTITION RANGE SINGLE3 INDEX FAST FULL SCAN (PCAR3)


3 - filter("SEASON_KEY"=2011)

Cost = 2

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SELECT COUNT(*) FROM pcarWHERE season_key IN ('2010','2011'); -- Combined

0 SELECT STATEMENT1 SORT AGGREGATE2 PARTITION RANGE INLIST3 TABLE ACCESS FULL (PCAR)


3 - filter("SEASON_KEY"=2010 OR "SEASON_KEY"=2011)

Cost = 27


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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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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';

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

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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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Online Partition Move 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

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Online Partition Move Consider the following example

CREATE TABLE pcar(



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;

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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

DBMS_PART.CLEANUP_ONLINE_OP (<schema>,<table>,<partition>);

Clean up failed operations on <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;

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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.

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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.

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Index Columns Consider the following table and global index

CREATE TABLE pcar(



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);

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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) LOCALINVISIBLE;

Index created *

ALTER INDEX pcar_global INVISIBLE;

ALTER INDEX pcar_local VISIBLE;

Switch the indexes

The new index (PCAR_LOCAL) is now visible The old index (PCAR_GLOBAL) can be dropped

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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

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Invisible Columns Consider the following table:

CREATE TABLE icar(


);

DESCRIBE icar

Name Null? TypeSEASON_KEY NUMBERRACE_KEY NUMBERDRIVER_KEY VARCHAR2(4)TEAM_KEY VARCHAR2(3)POSITION NUMBERLAPS_COMPLETED NUMBERRACE_POINTS NUMBER

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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$ uWHERE c.obj# = o.obj#AND o.owner# = u.user#AND u.name = 'GP‘AND o.name = 'ICAR';

NAME TYPE# COL# INTCOL# SEGCOL# PROPERTY

SEASON_KEY 2 1 1 1 0RACE_KEY 2 2 2 2 0DRIVER_KEY 1 3 3 3 0TEAM_KEY 1 4 4 4 0POSITION 2 5 5 5 0LAPS_COMPLETED 2 6 6 6 0RACE_POINTS 2 7 7 7 0

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Invisible Columns Make the LAPS_COMPLETED column invisible:

ALTER TABLE icar MODIFY laps_completed INVISIBLE;

DESCRIBE icar

Name Null? TypeSEASON_KEY NUMBERRACE_KEY NUMBERDRIVER_KEY VARCHAR2(4)TEAM_KEY VARCHAR2(3)POSITION NUMBERRACE_POINTS NUMBER

Describe the table again

The LAPS_COMPLETED column is now invisible

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Invisible Columns In the data dictionary COL$ now contains the following rows for ICAR:





0x400000000 = Invisible Column? 0x20 = Hidden Column

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Invisible Columns Make the LAPS_COMPLETED column visible again:

ALTER TABLE icar MODIFY laps_completed VISIBLE;

DESCRIBE icar

Name Null? TypeSEASON_KEY NUMBERRACE_KEY NUMBERDRIVER_KEY VARCHAR2(4)TEAM_KEY VARCHAR2(3)POSITION NUMBERRACE_POINTS NUMBERLAPS_COMPLETED NUMBER

The LAPS_COMPLETED column now appears at end of table

Describe the table again:

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Invisible Columns In the data dictionary COL$ now contains the following rows for ICAR:





LAPS_COMPLETED is now COL# 7

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Invisible Columns Why is this dangerous? Consider the following:

INSERT INTO icar VALUES (2013,1,'KRAI','LOT',1,58,25);

SEASON_KEY RACE_KEY DRIVER_KEY TEAM_KEY POSITION LAPS_COMPLETED RACE_POINTS

2013 1 KRAI LOT 1 58 25

SELECT * FROM icar;

ALTER TABLE icar MODIFY laps_completed INVISIBLE;

ALTER TABLE icar MODIFY laps_completed VISIBLE;

SEASON_KEY RACE_KEY DRIVER_KEY TEAM_KEY POSITION RACE_POINTS LAPS_COMPLETED

2013 1 KRAI LOT 1 25 582013 1 FALO FER 2 58 18

INSERT INTO icar VALUES (2013,1,'FALO','FER',2,58,18);

SELECT * FROM icar;

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Invisible Columns Continued...

ALTER TABLE icar MODIFY race_points INVISIBLE;

ALTER TABLE icar MODIFY race_points VISIBLE;

SEASON_KEY RACE_KEY DRIVER_KEY TEAM_KEY POSITION LAPS_COMPLETED RACE_POINTS

2013 1 KRAI LOT 1 58 252013 1 FALO FER 2 18 582013 1 SVET RBR 3 58 15

INSERT INTO icar VALUES (2013,1,‘SVET',‘RBR',3,58,15);

SELECT * FROM icar;

Column order is restored, but Fernando Alonso now has 58 points

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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

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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

GENERATED[ ALWAYS | BY DEFAULT [ ON NULL ] ]AS IDENTITY [ ( identity_options ) ]

Syntax is:

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 ) } . . .

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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 DRIVER_NAME DRIVER_DOB COUNTRY_KEY1 Sebastian Vettel 03-JUL-1987 GER2 Fernando Alonso 29-JUL-1981 SPA3 Kimi Raikkonen 17-OCT-1979 FIN

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Identity Clause DESCRIBE includes identity column

DESCRIBE driver2

Name Null? Type

DRIVER_KEY NOT NULL NUMBERDRIVER_NAME VARCHAR2(30)DRIVER_DOB DATECOUNTRY_KEY VARCHAR2(3)

No additional indexes are created

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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$ uWHERE c.obj# = o.obj#AND o.owner# = u.user#AND u.name = 'GP‘AND o.name = 'DRIVER2‘ORDER BY intcol#;


DRIVER_KEY 2 1 1 1 2800000000DRIVER_NAME 1 2 2 2 0DRIVER_DOB 12 3 3 3 0COUNTRY_KEY 1 4 4 4 0

0x800000000 = Default as Sequence 0x2000000000 = Generated ALWAYS identity column

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Identity Clause Default value for DRIVER_KEY column can be found in DBA_TAB_COLUMNS:

SELECT data_defaultFROM dba_tab_columnsWHERE owner = 'GP‘AND table_name = 'DRIVER2‘AND column_name = 'DRIVER_KEY';

"GP"."ISEQ$$_92584".nextval

SELECTsequence_owner AS owner,min_value,max_value,increment_by,cycle_flag,order_flag,cache_size

FROM dba_sequencesWHERE sequence_name = 'ISEQ$$_92584';

OWNER MIN_VALUE MAX_VALUE INCREMENT_BY C O CACHE_SIZE

GP 1 1.0000E+28 1 N N 20

In this example 92584 is the object ID of the GP.DRIVER2 table

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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

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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


2

SQL> CONNECT gp/gp


1

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Global TemporaryTable 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

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Global Temporary Table Undo 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

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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.

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Temporal Validity 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

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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 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');

Insert some data

Note: the above data is inaccurate

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Temporal Validity For example:

SELECT * FROM driver;

DRIVER_KEY TEAM_KEY JOINING_DATE LEAVING_DATEFALO FER 01-JAN-2010

FMAS FER 01-JAN-2006 31-DEC-2013 KRAI FER 01-JAN-2007 31-DEC-2009 RBAR FER 01-JAN-2000 31-DEC-2007

MSCH FER 01-JAN-1996 31-DEC-2006

SELECT * FROM driverAS OF PERIOD FOR team_member_valid_time TO_DATE (‘20-JUN-2009’);

DRIVER_KEY TEAM_KEY JOINING_DATE LEAVING_DATE FMAS FER 01-JAN-2006 31-DEC-2013 KRAI FER 01-JAN-2007 31-DEC-2009

Who was in the team for the 2009 British Grand Prix qualifying?

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Temporal Validity Describe the driver table

DESCRIBE driver

Name Null? TypeDRIVER_KEY VARCHAR2(4)TEAM_KEY VARCHAR2(3)JOINING_DATE DATELEAVING_DATE DATE

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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$ oWHERE c.obj# = o.obj#AND o.name = 'DRIVER3‘ORDER BY c.intcol#

NAME COL# INTCOL# SEGCOL# TYPE# PROPERTYTEAM_MEMBER_VALID_TIME 0 1 0 2 10028DRIVER_KEY 1 2 1 1 0TEAM_KEY 2 3 2 1 0JOINING_DATE 3 4 3 12 0LEAVING_DATE 4 5 4 12 0

0x10000 = Virtual Column 0x20 = Hidden Column 0x8 = Virtual Column

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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

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Extended Columns In Oracle 12c and above maximum column length has increased

Data Type 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

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Extended Columns By default attempts to create an extended column will fail:

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

MAX_STRING_SIZE parameter must be set to EXTENDED Default is value is STANDARD

ALTER TABLE car MODIFY notes VARCHAR2(32767);

*ERROR at line 1:

ORA-00910: specified length too long for its datatype

MAX_STRING_SIZE parameter cannot be updated when database is open:

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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

It is not possible to convert the MAX_STRING_SIZE parameter back from EXTENDED to STANDARD

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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 NUMBER,race_key NUMBER,driver_key VARCHAR2(4),team_key VARCHAR2(3),position NUMBER,laps_completed NUMBER,notes VARCHAR2(32767),race_points NUMBER

);

Alternatively maximum size of columns in existing tables can be increased:

ALTER TABLE car MODIFY notes VARCHAR2(32767);

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Extended Columns Extended columns are implemented as SECUREFILE LOBs

SELECT column_name,segment_name,securefileFROM dba_lobsWHERE 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_nameFROM dba_lobsWHERE owner = 'GP‘AND table_name = 'ECAR';

COLUMN_NAME INDEX_NAME

NOTES SYS_IL0000092626C00007$$

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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

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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

[ OFFSET offset { ROW | ROWS } ]

[ FETCH { FIRST | NEXT } [ { rowcount | percent PERCENT } ] { ROW | ROWS } { ONLY | WITH TIES } ]

Syntax is:

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

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Row Limiting Clause 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

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Row Limiting Clause Example – top ten drivers in 2012

Driver Name Points

Sebastian Vettel 281Fernando Alonso 278Kimi Raikkonen 207Lewis Hamilton 190Jenson Button 188Mark Webber 179Felipe Massa 122Romain Grosjean 96Nico Rosberg 93Sergio Perez 66

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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 tWHERE c.season_key = 2012AND c.driver_key = d.driver_keyAND c.team_key = t.team_keyGROUP BY d.driver_name,t.team_nameORDER BY SUM(c.driver_points) DESC

)WHERE ROWNUM <= 5;

-----------------------------------------------------------------------| 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)|-----------------------------------------------------------------------

Driver Name

Points

Sebastian Vettel

281Fernando Alonso

278Kimi Raikkonen

207Lewis Hamilton

190Jenson Button

188

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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 tWHERE c.season_key = 2012AND c.driver_key = d.driver_keyAND c.team_key = t.team_keyGROUP BY d.driver_name,t.team_nameORDER BY SUM(c.driver_points) DESCFETCH FIRST 5 ROWS ONLY;

-------------------------------------------------------------------------| 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)|-------------------------------------------------------------------------

Driver Name

Points

Sebastian Vettel

281Fernando Alonso

278Kimi Raikkonen

207Lewis Hamilton

190Jenson Button

188

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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 tWHERE c.season_key = 2012AND c.driver_key = d.driver_keyAND c.team_key = t.team_keyGROUP BY d.driver_name,t.team_nameORDER BY SUM(c.driver_points) DESCFETCH FIRST 20 PERCENT ROWS WITH TIES;

-----------------------------------------------------------------------| 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)|-----------------------------------------------------------------------

Driver Name

Points

Sebastian Vettel

281Fernando Alonso

278Kimi Raikkonen

207Lewis Hamilton

190Jenson Button

188

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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 tWHERE c.season_key = 2012AND c.driver_key = d.driver_keyAND c.team_key = t.team_keyGROUP BY d.driver_name,t.team_nameORDER BY SUM(c.driver_points) DESCOFFSET 5 ROWSFETCH FIRST 5 ROWS ONLY;

-------------------------------------------------------------------------| 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)|-------------------------------------------------------------------------

Driver Name

Points

Mark Webber

179Felipe Massa

122Romain Grosjean

96Nico Rosberg

93Sergio Perez

66

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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.

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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_KEY492

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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_histogramsWHERE owner = ‘GP’ AND table_name = ‘CAR’AND column_name = ‘DRIVER_KEY’;

COUNT (*)2

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Histograms Collect histograms on the DRIVER_KEY column



method_opt => 'FOR COLUMNS driver_key');


COUNT (*)75

Default behaviour is to create a maximum of 256 buckets

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Histograms If more than 256 buckets are required, this must be specified explicitly:



method_opt => 'FOR COLUMNS driver_key SIZE 2048');


COUNT (*)492

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Histograms Multi-Column Statistics

DECLAREl_extension_name VARCHAR2(30);

BEGINl_extension_name := dbms_stats.create_extended_stats(

ownname => 'GP',tabname => 'CAR6',extension => '(driver_key,team_key)‘

);END;

BEGINdbms_stats.gather_table_stats(

ownname => 'GP',tabname => 'CAR6',estimate_percent => NULL,method_opt => 'FOR COLUMNS (DRIVER_KEY,TEAM_KEY) SIZE 2048‘

);END;

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DECLAREl_extension_name VARCHAR2(30);

BEGINl_extension_name := dbms_stats.create_extended_stats(

ownname => 'GP',tabname => 'CAR6',extension => '(driver_key,team_key)‘

);END;

BEGINdbms_stats.gather_table_stats(

ownname => 'GP',tabname => 'CAR6',estimate_percent => NULL,method_opt => 'FOR COLUMNS (DRIVER_KEY,TEAM_KEY) SIZE 2048‘

);END;

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76

Id

Operation Name Rows Bytes Cost (%CPU)

Time

0 SELECT STATEMENT 1 939(0)

00:00:01

1 SORT AGGREGATE

1 9

2 TABLE ACCESS FULL

CAR 181 162939 (0)

00:00:01

SELECT COUNT(*) FROM gp.carWHERE driver_key = ‘MSCH'AND team_key = 'FER';

COUNT(*)181

Correct Cardinality

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77

Id

Operation Name Rows Bytes Cost (%CPU)

Time

0 SELECT STATEMENT 1 939(0)

00:00:01

1 SORT AGGREGATE

1 9

2 TABLE ACCESS FULL

CAR 1 162939 (0)

00:00:01

SELECT COUNT(*) FROM gp.carWHERE driver_key = ‘MSCH'AND team_key = ‘JOR';

COUNT(*)1

Correct Cardinality

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Application ContinuityThis 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.

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Application Continuity 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

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Application Continuity 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

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Application Continuity Must connect to a user-defined service

Not the database service E.g. for single instance database

DECLAREl_arr DBMS_SERVICE.SVC_PARAMETER_ARRAY;

BEGINl_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

srvctl start service –d TEST –s SERVICE1 –i TEST1

Remember to start the service...

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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)))

REMOTE_LISTENER database parameter must include SCAN name if clients specify SCAN names Node names if clients specify address list

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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();

Requires $ORACLE_HOME/jdbc/lib/ojdbc6.jar on CLASSPATH

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Application Continuity Debugging replayable connections

Add $ORACLE_HOME/jdbc/lib/ojdbc6_g.jar to the CLASSPATH

java -Djava.util.logging.config.file=/home/oracle/appcon/properties J7

Execute using:

Writes trace to replay_0.trc.0

Add the following to the properties file

oracle.jdbc.internal.replay.level = FINESThandlers = java.util.logging.FileHandlerjava.util.logging.FileHandler.pattern = /home/oracle/12c/appcon2/replay_%U.trcjava.util.logging.FileHandler.limit = 500000000java.util.logging.FileHandler.count = 1000java.util.logging.FileHandler.formatter = java.util.logging.XMLFormatter

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Application Continuity 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

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Thank You For Your Interest

[email protected]

Juliandyke.com 1 © 2013 - Julian Dyke Web Version Oracle 12c New Features.

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