DBA Commands and Concepts That Every Developer Should Know

DBA COMMANDS
AND CONCEPTS
THAT EVERY
DEVELOPER
SHOULD KNOW
Alex Zaballa

Copyright © 2016 Accenture All rights reserved. | 2
Alex Zaballa
http://alexzaballa.blogspot.com/
@alexzaballa
https://www.linkedin.com/in/alexzaballa
235 and counting…

Worked for 3 years in Brazil as a Clipper/Delphi Developer (15 years old)
1997-1999
Worked for 7 years in Brazil as an Oracle Developer
2000 - 2007
Worked for 8 years in Angola as an Oracle DBA
for the Ministry of Finance.
2007 - 2015

http://www.guobtechday2017.eventize.com.br/

Desenvolvedores
vs
DBAs

EXPLAIN PLAN

EXPLAIN PLAN
Are you using Explain Plan ?

EXPLAIN PLAN
Explain Plan Lies

EXPLAIN PLAN
Explain Plan just try to predict the Plan.
AUTOTRACE experiences a similar "problem”,
especially when the SQL statement uses bind
variables.

EXPLAIN PLAN
Explain plan is blind to:
• Bind Variable Peeking
• Adaptive Features
• Etc

EXPLAIN PLAN
Now what?
• DBMS_XPLAN.DISPLAY_CURSOR
• V$SQL_PLAN%

DBMS_XPLAN.DISPLAY_CURSOR

• SQL_ID
• CURSOR_CHILD_NO (default 0)
• FORMAT
 TYPICAL = DEFAULT
 ALL = TYPICAL + QB + PROJECTION + ALIAS +
REMOTE
 ADVANCED = ALL + OUTLINE + BINDS
 ALLSTATS = IOSTATS + MEMSTATS (all executions)
 ALLSTATS LAST (last execution)
 ADAPTIVE (12c)

DBMS_XPLAN
• DISPLAY (from PLAN_TABLE)
• DISPLAY_CURSOR
• DISPLAY_AWR
• DISPLAY_SQL_PLAN_BASELINE
• DISPLAY_SQL_SET
SELECT * FROM
TABLE(DBMS_XPLAN.DISPLAY_CURSOR('sql_id',child,'ADVANCED'));

By Carlos Sierra

https://blogs.oracle.com/optimizer/entry/how_do_i_know_if
/*+ gather_plan_statistics */
or
Alter session set statistics_level = ALL

SQL MONITOR

SQL MONITOR
• Oracle Enterprise Manager
• EM Database Express (12c)
• SQL Developer
• Linha de Comando

SQL MONITOR
select dbms_sqltune.report_sql_monitor(
sql_id => 'gjabwvvr07w09',
report_level=>'ALL',
type => 'ACTIVE')
from dual;

SQLT / SQLTXPLAIN

SQLT / SQLTXPLAIN
SQLT Diagnostic Tool (Doc ID 215187.1)
Pros
• Oracle Support Standard
• Free (requires MOS account)
• Comprehensive and mature
Cons
• Requires installation
• HTML Tables (no charts)

SQLD360

COST OF AN INDEX

FULL TABLE SCAN

FULL TABLE SCAN
https://www.slideshare.net/MauroPagano3/
full-table-scan-friend-or-foe

FULL TABLE SCAN

FULL TABLE SCAN
https://richardfoote.wordpress.com/2008/05/12/index-scan-
or-full-table-scan-the-magic-number-magic-dance/

FULL TABLE SCAN
https://richardfoote.wordpress.com/2008/05/12/index-scan-
or-full-table-scan-the-magic-number-magic-dance/
• Clustering Factor  How well ordered the rows in the table are in
relation to the index.
• Selectivity of the query
• Number of table blocks
• Effective multiblock read count
• Relative cost of single vs. multiblock I/Os
• Parallelism
• Etc

FULL TABLE SCAN

FULL TABLE SCAN
• Not always good
• Not always bad

ANALYZING TABLES

ANALYZING TABLES
https://docs.oracle.com/cd/B19306_01/server.102/b14200/
statements_4005.htm

PENDING STATISTICS

PENDING STATISTICS
We have the option of keeping the newly gathered statistics in a pending state for testing purposes,
until you choose to publish them.
Set table preferences:
begin
dbms_stats.set_table_prefs (
ownname => 'SCOTT',
tabname => 'EMP',
pname => 'PUBLISH',
pvalue => 'FALSE'
);
end;
Collect the statistics.

PENDING STATISTICS

PENDING STATISTICS
If it’s ok:
Or:

RESTORE STATISTICS FROM HISTORY

Check the retention:
Default is 31 days.

Statistics available for the table:

Restore:

INVISIBLE INDEXES

INVISIBLE INDEXES
OR

PARALLEL DML

PARALLEL DML
insert /*+ append parallel */ into tab1 select /*+ parallel */ *
from tab2 nologging;
15 minutes to complete.
create table tab1 as select /*+ parallel */ * from tab2
nologging;
2 minutes to complete.

PARALLEL DML

ORACLE FLASHBACK QUERY

ORACLE FLASHBACK QUERY
Retrieve old versions of procedures:

DBMS_APPLICATION_INFO

DBMS_APPLICATION_INFO
Allows programs to add information to the
V$SESSION.
Use SET_MODULE to set the name for the program that the
user is currently executing. Optionally you can also set an
action name.
Use SET_ACTION for subsequent processing.
Use SET_CLIENT_INFO for any additional information.

SCHEMA MANAGEMENT
DDL WAIT OPTION

SCHEMA MANAGEMENT
DDL WAIT OPTION
SQL> alter table invoice add (code number);
alter table invoice add (code number)
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT
specified or timeout expired

SCHEMA MANAGEMENT
DDL WAIT OPTION
Parameter DDL_LOCK_TIMEOUT (default = 0)
It will wait for N seconds.
In that N seconds, it continually re-tries the DDL operation
until it's successful or this time expires.

ADDING COLUMNS WITH A DEFAULT VALUE

ADDING COLUMNS WITH A DEFAULT VALUE
The table SALES is about 400 million rows.
10.2.0.4.0  alter table sales add tax varchar2(2) default ‘XX’
not null;
Elapsed: 00:41:00.00
11.2.0.4.0  alter table sales add tax varchar2(2) default ‘XX’
not null;
Elapsed: 00:00:00.03

COUNT(1) VS COUNT(*)

COUNT(1) VS COUNT(*)
What is the difference between count(1) and count(*) ?
Nothing!

12.1 AND 12.2

READ OBJECT PRIVILEGE AND READ ANY TABLE
SYSTEM PRIVILEGE

SYSTEM PRIVILEGE
What is the difference to SELECT and SELECT ANY
TABLE?

SYSTEM PRIVILEGE
SELECT and SELECT ANY TABLE provides the ability to
lock rows:
LOCK TABLE table_name IN EXCLUSIVE MODE;
SELECT ... FROM table_name FOR UPDATE;

SYSTEM PRIVILEGE
SQL> grant select on scott.emp to teste;
Grant succeeded.
SQL> lock table scott.emp in exclusive mode;
Table(s) Locked.

SYSTEM PRIVILEGE
SQL> grant read on scott.emp to teste;
Grant succeeded.
SQL> lock table scott.emp in exclusive mode;
lock table scott.emp in exclusive mode
*
ERROR at line 1:
ORA-01031: insufficient privileges

EXTENDED DATA TYPES

EXTENDED DATA TYPES
SQL> create table tabela_teste(campo01 varchar2(4001));
*
ERROR at line 1:
ORA-00910: specified length too long for its datatype

EXTENDED DATA TYPES
• VARCHAR2 : 32767 bytes
• NVARCHAR2 : 32767 bytes
• RAW : 32767 bytes

EXTENDED DATA TYPES
SHUTDOWN IMMEDIATE;
STARTUP UPGRADE;
ALTER SYSTEM SET max_string_size=extended;
@?/rdbms/admin/utl32k.sql
SHUTDOWN IMMEDIATE;
STARTUP;
**Once you switch to extended data types you can't switch back

PL/SQL FROM SQL

TEMPORARY UNDO

TEMPORARY UNDO
ALTER SESSION SET TEMP_UNDO_ENABLED = TRUE;
ALTER SYSTEM SET TEMP_UNDO_ENABLED = TRUE;

LONGER IDENTIFIER NAMES

Starting with Oracle Database 12c Release 2 (12.2), the
maximum length of identifier names for most types of
database objects has been increased to 128 bytes.

PDB LOCKDOWN PROFILES

PDB LOCKDOWN PROFILES
A security mechanism to restrict operations that are available
to local users connected to a specified PDB.

SQLCL
http://www.oracle.com/technetwork/developer-tools/sqlcl/downloads/index.html

QUESTIONS?

Thank You
Slides Available: http://www.slideshare.net/

DBA Commands and Concepts That Every Developer Should Know

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