Oracle Database 12c - The Best Oracle Database 12c Tuning Features for Developers and DBAs

Oracle Database 12c
The Best Oracle Database 12c
Tuning Features for Developers
and DBAs
Presented by: Alex Zaballa, Oracle DBA

Alex Zaballa
http://alexzaballa.blogspot.com/
@alexzaballa147 and counting…
https://www.linkedin.com/in/alexzaballa

Worked for 7 years in Brazil as a Developer
Worked 8 years for the Ministry of Finance
In Angola as a DBA
March - 2007 until March - 2015

Oracle Database 12c
The Best Oracle Database 12c Tuning Features for
Developers and DBAs

Oracle Official Documentation
12.1.0.2
• http://docs.oracle.com/database/121/NEWFT
/chapter12102.htm
Oracle Learning Library (OLL)
• https://apexapps.oracle.com/pls/apex/f?p=44
785:1:0

Articles about 12c
• https://oracle-base.com/articles/12c/articles-
12c
• http://www.oraclealchemist.com/news/install
-oracle-12c-12-1/
• http://www.profissionaloracle.com.br/

“With more than 500 new features, Oracle
Database 12c is designed to give Oracle
customers exactly what they’ve told us they
need for cloud computing, big data, security,
and availability.”

Multitenant
Source: Oracle Documentation

Multitenant
Is it a Tuning Feature?

Multitenant
Source: https://blogs.oracle.com/UPGRADE/entry/non_cdb_architecture_of_oracle

In-Memory

In-Memory
SIMD Vector Processing
Source: http://www.oracle.com/technetwork/database/in-memory/overview/twp-
oracle-database-in-memory-2245633.html

In-Memory
Is it a Tuning Feature?
“Using Database In-Memory, businesses can instantaneously
run analytics and reports that previously took hours or days.”

In-Memory
In-Memory Area – a static pool in SGA

In-Memory
Source: OracleBase.com

In-Memory
Alter table hr.EMPLOYEES inmemory;
ALTER TABLE sales MODIFY PARTITION SALES_Q1_1998
NO INMEMORY;
ALTER TABLE sales INMEMORY NO INMEMORY(prod_id);
CREATE TABLESPACE tbs_test
DATAFILE '+DG01 SIZE 100M
DEFAULT INMEMORY;

In-Memory
Source: http://www.oracle.com/technetwork/database/in-memory/overview/twp-
oracle-database-in-memory-2245633.html

SQL Query Row Limits and Offsets

Top-N Queries – Pré 12c
select * from ( select codigo, nome, salario
from tabela_teste
order by salario desc)
where rownum <= 5

select codigo, nome, salario
from tabela_teste
order by salario desc
FETCH FIRST 5 ROWS ONLY

from tabela_teste
order by salario
FETCH FIRST 30 PERCENT ROWS ONLY

from tabela_teste
order by salario desc
OFFSET 2 ROWS FETCH NEXT 2 ROWS ONLY;

Approximate Count Distinct
This function provides an alternative to the COUNT (DISTINCT
expr), with negligible deviation from the exact result.

PL/SQL From SQL
with
function Is_Number
(x in varchar2) return varchar2 is
Plsql_Num_Error exception;
pragma exception_init(Plsql_Num_Error, -06502);
begin
if (To_Number(x) is NOT null) then
return 'Y';
else
return '';
end if;
exception
when Plsql_Num_Error then
return 'N';
end Is_Number;
select rownum, x, is_number(x) is_num from t;

Session Level Sequences
Session level sequences are used to produce
unique values in a session. Once the session
ends, the sequence is reset.
Generating Primary Keys for a Global Temporary
Table would be a field where those kinds of
sequences could be used.

CREATE SEQUENCE sequence_teste
START WITH 1
INCREMENT BY 1
SESSION
/

ALTER SEQUENCE sequence_teste
SESSION;
ALTER SEQUENCE sequence_teste
GLOBAL;

Session private statistics for Global
Temporary Tables
Pre 12c, statistics gathered for global temporary
tables (GTTs) were common to all sessions.

Temporary Tables
On 12c, by default session-private statistics are
enabled
SELECT DBMS_STATS.get_prefs('GLOBAL_TEMP_TABLE_STATS')
FROM dual;
STATS
------------------------------------------------------------------------------
SESSION

Temporary Tables
How to change?
Behavior pre 12c:
BEGIN
DBMS_STATS.set_global_prefs (
pname => 'GLOBAL_TEMP_TABLE_STATS',
pvalue => 'SHARED');
END;
/
Back to default on 12c:
BEGIN
DBMS_STATS.set_global_prefs (
pname => 'GLOBAL_TEMP_TABLE_STATS',
pvalue => 'SESSION');
END;
/

Temporary Tables
How to change for one table?
BEGIN
dbms_stats.set_table_prefs('SCOTT','GTT_TESTE',
'GLOBAL_TEMP_TABLE_STATS','SHARED');
END;
BEGIN
dbms_stats.set_table_prefs('SCOTT','GTT_TESTE',
'GLOBAL_TEMP_TABLE_STATS’,’SESSION');
END;

Temporary Undo
Global Temporary Tables (GTT) hold the data in a
temporary tablespace. The data in GTTs are either
deleted after commit or kept until the session is
connected depending of the definition of the
GTT.(ON COMMIT PRESERVE OR DELETE ROWS ).
DMLs in a Global Temporary Tables do not generate
REDO, but generate UNDO and this will result in
REDO generating.

Temporary Undo
alter session set temp_undo_enabled=true;
alter system set temp_undo_enabled=true;
**you can change for the session or for the database.
*default true

Multiple Indexes on the same set of
Columns
Pre 12c:
ORA-01408: such column list already indexed
error.

Columns
Is the ability to create more than one index on
the same set of columns in 12c.
**Only one of these indexes can be visible at a
time

Columns
Why would you want to do that?
• Unique versus nonunique
• B-tree versus bitmap
• Different partitioning strategies

Limit the PGA
SQL> show parameter pga
NAME TYPE VALUE
-------------------------- ------------- ----------------------
pga_aggregate_limit big integer 2G

Limit the PGA
PGA_AGGREGATE_LIMIT is set to the greater of:
- 2 GB (default value)
- 200% of PGA_AGGREGATE_TARGET
- 3 MB times the PROCESSES parameter

Statistics During Loads
The ability to gather statistics automatically
during bulk loads:
- CREATE TABLE AS SELECT
- INSERT INTO ... SELECT into an empty table
using a direct path insert

Partial Indexes for Partitioned Table
• You can create local and global indexes on a
subset of the partitions of a table, enabling
more flexibility in index creation.
• This feature is not supported for unique
indexes, or for indexes used for enforcing
unique constraints.

Partial Indexes for Partitioned Table

Full Database Caching
Can be used to cache the entire database in
memory. It should be used when the buffer
cache size of the database instance is greater
than the whole database size.

Adaptive Query Optimization

Adaptive Plans

Adaptive Join Method

Optimizer can change join from Nested Loop to
Hash Join and vice versa.
Why?
Optimizer mistakes
 Estimated Rows and Actual rows are different
Before 12c requires DBA/Developer intervention

Parameters that control Adaptive Plans:
Name Type Value
optimizer_adaptive_features boolean TRUE
optimizer_adaptive_reporting_only boolean FALSE
optimizer_features_enable string 12.1.0.1

Explain Plan command shows the
default plan

DBMS_XPLAN.DISPLAY_CURSOR
shows the final plan

Real-Time SQL Monitoring
• Sql Monitoring requires both Diagnostics and
Tuning Pack licenses

• MONITOR Hint
SELECT /*+ MONITOR */
• All parallel statements
• After 5 seconds of CPU/IO time spent for serial
queries

SPOOL /tmp/report_sql_monitor.htm
SELECT DBMS_SQLTUNE.report_sql_monitor(
sql_id => '5dhu4w0j59yp7',
type => 'HTML',
report_level => 'ALL') AS report
FROM dual;
SPOOL OFF

Oracle Announces Beta Availability of Oracle Database 12c Release 2 - Oct 26,
2015
• PLUGGABLE DATABASES
From 252 to 4096
• HOT CLONING
Don’t need to put the source in read-only for cloning
• SHARDING
It’s like partitioning in a shared nothing database
The data is split into multiple databases
• In-Memory
In-Memory column Store on Active Data Guard
Heat Map
• APPLICATION CONTAINER
Pluggable Databases will share application objects
• More isolation, resource manager will limit the memory in addition to CPU and I/O.
• AWR will work on Active Data Guard Database: you can tune your reporting database
Oracle Database 12.2

Availability of Oracle Database 12.2
Source: https://blogs.oracle.com/UPGRADE/entry/oracle_database_12_2_just

Oracle Database Release Status
MOS Note:742060.1

Oracle Database 12c - The Best Oracle Database 12c Tuning Features for Developers and DBAs

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