Database & Technology 1 _ Milina Ristic _ Why use oracle data guard.pdf

The most comprehensive Oracle applications & technology content under one roof The most comprehensive Oracle applications & technology content under one roof

Why Use Oracle Data Guard?

Milina Ris7c TelstraClear, New Zealand

The most comprehensive Oracle applications & technology content under one roof

Data Guard Func,ons

•  High availability •  Data protec,on •  Disaster recovery •  Repor,ng •  Backup and recovery


Data Guard Configura,ons

•  Physical Standby – block for block iden,cal copy of primary database

•  Logical Standby – same logical informa,on as primary database


Data Guard 11g

Snapshot Standby •  fully updateable standby database •  tes,ng on produc,on like data •  easily resynchronised with produc,on


Data Guard 11g

Ac,ve Data Guard •  Real-‐,me repor,ng •  Fast incremental backups •  Automa,c correc,on of corrupted blocks

NB: Requires separate license


Ac,ve Data Guard

Read-‐only applica,on can perform: •  Selects •  Alter session •  Call stored procedures •  Call remote procedures via DB links •  DB links to write to remote databases


Apply Lag Management 11g

ALTER SESSION SET STANDBY_MAX_DATA_DELAY=600;

ORA-‐03172: STANDBY_MAX_DATA_DELAY of 600 seconds exceeded


Physical Standby

Primarydatabase

Standbydatabase

Database Database copy

Redotransport


Benefits of Physical Standby

•  Switchover •  Failover •  Repor,ng •  Backup


Running Backup on Physical Standby

Primary •  4-‐node RAC •  NetApp Filers •  No ASM •  RMAN •  TSM with TDPO

Standby •  4-‐node RAC •  SAN •  ASM •  RMAN •  TSM with TDPO


Filesystem to ASM and Back

How to duplicate a controlfile when ASM is involved [ID 345180.1]

How to move a datafile from a file system to ASM [ID 390274.1]

How to move a datafile from ASM to the file system [ID 390416.1]


Primary RAC database

Standby RAC database Primary Recovery Catalog

Secondary Recovery Catalog

backup

resy

nc


Alterna,ves for DR

Complex systems e.g. Sybase database Oracle Transparent Gateway for Sybase Third party applica,ons

may require alterna,ve technologies: •  SAN replica,on •  snapshot technology


Logical Standby Primary

databaseStandbydatabase

Log Transport Services

Log Apply Services

Oracle N

et

Archived Redo Log Files

Archived Redo Log Files


SQL Apply – Log Mining

•  READER – reads archived redo logs •  PREPARER – generates logical change records •  BUILDER – groups LCRs into transac,ons


SQL Apply – Apply Processing

•  ANALYZER – iden,fies dependencies •  COORDINATOR – assigns transac,ons •  APPLIER – applies transac,ons


Benefits of Logical Standby

•  Switchover •  Failover •  Repor,ng •  Addi,onal objects


Importance of NOT NULL

TABLE1 ID NUMBER(5) NAME VARCHAR2(20) TABLE2 ID NOT NULL NUMBER(5) NAME VARCHAR2(20)


Importance of NOT NULL

UPDATE SQL on standby database UPDATE table1 SET name = 'Smith' WHERE (id = :b1 OR id IS NULL) AND (name = :b2 OR name IS NULL)


Tracing APPLIER

SELECT PID, TYPE, STATUS, HIGH_SCN FROM V$LOGSTDBY oradebug setospid <APPLIER pid> oradebug unlimit oradebug event 10046 trace name context forever, level 12


Tracing APPLIER

oradebug setospid <APPLIER pid> oradebug event 10046 trace name context off Trace file will be generated in bdump tkprof <fn> tkprof.out explain= \"/ as sysdba\"


Data Guard Modes

ALTER DATABASE GUARD {ALL|STANDBY|NONE} ALL – read only STANDBY – read only for maintained objects NONE – fully updateable


Bulk Updates

Primary Single update of million rows Standby Million updates on standby


Reinstan,a,ng Tables

DBMS_LOGSTDBY.INSTANTIATE_TABLE ('HR', 'EMPLOYEES', 'primary_dblink');

•  Log apply needs to be stopped •  Table is dropped and recreated •  Addi,onal grants and indexes are lost


To Skip or Not to Skip

•  Temporary and audit tables •  User crea,on •  Schemas •  Index rebuilds •  Par,,on maintenance


Par,,on Maintenance

Produc7on •  Keep 12 months •  Archive older data •  Drop older par,,ons

Repor7ng •  Keep 24 months •  Drop older par,,ons


Skipping Transac,ons

execute dbms_logstdby.skip ('SCHEMA_DDL', 'HR', 'DEPT'); ('DML', 'HR', '%TEMP'); ('ALTER INDEX', '%', '%');


Skipping Drop Par,,on

execute dbms_logstdby.skip ('ALTER TABLE', '<schema name>', '<object name>', '<procedure name>');


Skipping Drop Par,,on

IF upper(statement) like '%DROP%PARTITION%' THEN skip_ac,on := sys.dbms_logstdby.SKIP_ACTION_SKIP; ELSE skip_ac,on := sys.dbms_logstdby.SKIP_ACTION_APPLY;

END IF;


Hints – What to Watch Out For

•  Explicitly using inappropriate indexes •  Hin,ng full table scan •  Using too high parallel degree


Unsupported Opera,ons

Table compression up to 11gR2 workaround – triggers

Segment shrinking workaround – move


Logical Standby Tips

•  Sound primary database data model •  Beware bulk updates •  Know the limits •  Op,mise long running processes


Q&A

[email protected]