Client Connectivity in a DataGuard Environment Harald van Breederode Oracle University 4-DEC-2007

Transcription

1 Client Connectivity in a DataGuard Environment Harald van Breederode Oracle University 4-DEC

2 About Me Senior Principal DBA Trainer Oracle University 25 years Unix Experience 12 years Oracle DBA Experience Oracle8i, 9i, 10g and 11g OCP Oracle10g OCM DBA Certification Exam Team Reviewer DBA Curriculum Development Reviewer Enterprise Linux Certification Exam Global Lead Visually Impaired (Legally Blind) 2

3 Agenda Introduction What is DataGuard Types of DataGuard Databases Role Management Services The Client Connection Problem The Solution Sample Implementation Demonstration Questions & Answers 3

4 What is DataGuard High Availability and DR Solution One or more additional databases at remote locations These are called Standby Databases They may be local for proof of concept DataGuard == Standby Database plus extra s: DataGuard Broker Grid Control Management Interface CLI Management Interface Role Management Services 4

5 Types of DataGuard Databases There are four types of DataGuard Databases: Primary Database The Database that needs protection Transports Redo to its Standby Databases Physical Standby Database Exact physical copy of primary database May be opened read only Real Time Query permits redo apply whilst open Read Only 11g Synchronized with primary using Redo Apply 5

6 Types of DataGuard Databases (continued) Snapshot Standby Database 11g Physical Standby Database opened temporarily for Read Write Used for Real Application Testing (RAT) Logical Standby Database Logical copy of primary database Is Read Write open for normal usage Synchronized with primary using SQL Apply Important for Rolling Release Upgrade 6

7 Role Management Services DataGuard Database roles may change dynamically Switchover A planned Role change Primary and One Standby switch roles Used for maintenance on the Primary Always Initiated by the DBA Failover An unplanned Role change Used when the Primary is broken or unreachable due to network issues Can happen automatically with Fast-Start Failover Snapshot Standby Activation or Deactivation RTQ Standby Activation or Deactivation 7

8 Question How do clients connect to databases generally and what special considerations exist in DataGuard configurations? Note: The term Client is used generically. It can be anything connecting to a Database Instance: Traditional Client Server applications or Middle Tiers 8

9 General Client Connectivity Server side: PMON registers its instance with listeners Client side: connect NetServiceName gets resolved to a TNS entry Client sends connection request to a listener Listener hands connection off to : Dedicated server process Dispatcher process V1110 = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = PRUTSER)(PORT = 1521)) (CONNECT_DATA = (SERVICE_NAME = V1110))) 9

10 DataGuard Client Connectivity Issues As there are two or more databases in a DataGuard configuration, clients must know on which hosts these databases reside. Therefore TNS Entries must have a CONNECTION_LIST section containing all hosts participating in the DataGuard configuration V1110 = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = PRUTSER)(PORT = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = EL5)(PORT = 1521)) (CONNECT_DATA = (SERVICE_NAME = V1110))) 10

11 Question What happens if connection requests go to the wrong host or Database? 11

12 Connecting to the Wrong Database If Clients send connection requests to the wrong host they may be connected to the wrong database or connection errors may occur. Possible Connection Error ORA-01033: ORACLE initialization or shutdown in progress Potential Connections to Wrong Databases RTQ instead of Primary Logical Standby instead of Primary Snapshot Standby instead of Primary Primary instead of Snapshot Standby Primary instead of RTQ Primary instead of Logical Standby Plus several other possibilities 12

13 Question How can one prevent clients from connecting to the wrong Database? 13

14 Use Database Services Database Services act as an abstraction layer between the Client and Database Instances Primarily used for Workload Management RAC and Single Instance Databases use them Services are registered with Listeners Clients connect to Services instead of Instances Listeners use registration details to determine which instance(s) support(s) a particular service Can be used as a tuning dimension V$SERVICE_STAT V$SERVICE_EVENT Can be used to trace sessions DBMS_MONITOR package 14

15 Service Attributes A Service has several attributes: A Service Name for Administration purposes A Network Name for Services that are meant for external Client Connections Transparent Application Failover attributes for Client Connections that should be TAF enabled 15

16 Managing Services Services are managed with the DBMS_SERVICE package. The following actions can be performed: Create Start Modify Stop Delete Note: This discussion is limited to Single Instance usage 16

17 Creating the Services The Service for the Primary Database: DBMS_SERVICE.CREATE_SERVICE( - SERVICE_NAME => 'DG_PROD', - NETWORK_NAME => 'DG_PROD', - FAILOVER_METHOD => 'BASIC', - FAILOVER_TYPE => 'SELECT', - FAILOVER_RETRIES => 180, - FAILOVER_DELAY => 1); 17

18 Creating the Services (continued) The Service for the Real Time Query Database DBMS_SERVICE.CREATE_SERVICE( - SERVICE_NAME => 'DG_RTQ', - NETWORK_NAME => 'DG_RTQ'); The Service for the Logical Standby Database DBMS_SERVICE.CREATE_SERVICE( - SERVICE_NAME => 'DG_LSD', - NETWORK_NAME => 'DG_LSD'); The Service for the Snapshot Standby Database DBMS_SERVICE.CREATE_SERVICE( - SERVICE_NAME => 'DG_RAT', - NETWORK_NAME => 'DG_RAT'); 18

19 Question How can we control Database Services so that clients are guaranteed connections to the correct database in the DataGuard Configuration? 19

20 Use a Database Event Trigger Event Triggers were introduced in Oracle We Require the AFTER STARTUP Trigger: Invoked when ALTER DATABASE OPEN occurs Can check DATABASE_ROLE in V$DATABASE Can check OPEN_MODE in V$DATABASE Should use DBMS_SERVICE package to start the appropriate service 20

21 Use a Database Event Trigger (continued) Based on Service names defined earlier the Trigger must start Services as follows: DG_PROD on the Primary DG_RTQ when the Physical Standby is opened Read Only DG_LSD on a Logical Standby DG_RAT when a Physical Standby is converted to a Snapshot Standby 21

22 Demo AFTER STARTUP Trigger CREATE TRIGGER MANAGE_SERVICES AFTER STARTUP ON DATABASE DECLARE BEGIN END; / ROLE VARCHAR(30); OMODE VARCHAR(30); SELECT DATABASE_ROLE INTO ROLE FROM V$DATABASE; SELECT OPEN_MODE INTO OMODE FROM V$DATABASE; IF ROLE = 'PRIMARY' THEN DBMS_SERVICE. START_SERVICE ('DG_PROD'); ELSIF ROLE = 'PHYSICAL STANDBY' THEN IF OMODE = 'READ ONLY' THEN DBMS_SERVICE. START_SERVICE ('DG_RTQ'); END IF; ELSIF ROLE = LOGICAL STANDBY' THEN DBMS_SERVICE. START_SERVICE ('DG_LSD'); ELSIF ROLE = 'SNAPSHOT STANDBY' THEN END IF; DBMS_SERVICE. START_SERVICE ('DG_RAT'); 22

23 Question Now that we can control which services are started in which database instances, how do we guarantee that clients can connect? 23

24 Use Appropriate TNS Entries PROD = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = prutser)(port = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = el5)(port = 1521)) (CONNECT_DATA = (SERVICE_NAME = DG_PROD))) RTQ = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = prutser)(port = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = el5)(port = 1521)) (CONNECT_DATA = (SERVICE_NAME = DG_RTQ))) RAT = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = prutser)(port = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = el5)(port = 1521)) (CONNECT_DATA = (SERVICE_NAME = DG_RAT))) LSD = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = prutser)(port = 1521)) (ADDRESS = (PROTOCOL = TCP)(HOST = el5)(port = 1521)) (CONNECT_DATA = (SERVICE_NAME = DG_LSD))) 24

25 Demonstration The demo environment consists of: Virtual Machine PRUTSER OEL4 Virtual Machine EL5 OEL5 Oracle Database 11g Database Name V1110 DataGuard is already configured All demos are scripted To request these demo scripts please me at: 25

26 Scenario #1 and #2 Connecting to a DataGuard configuration without using Database Services Based on randomness we either get: The connection we desire or An ORA-01033: init or shutdown in progress Connecting to the Primary in a DataGuard configuration using a TAF Enabled Database Service Once connected we perform a switchover 26

27 Scenario #3 and #4 Connecting to a Snapshot Standby in a DataGuard configuration using a Database Service First without a Snapshot Standby Second with a Snapshot Standby Connecting to a Physical Standby opened Read Only in a DataGuard configuration using a Database Service First without a Read Only opened Physical Standby Second with a Read Only opened Physical Standby 27

28 Q U E S T I O N S & A N S W E R S 28

29 Final words Thank You for your kind attention! I will be at the Oak Table from time to time during the conference for further discussion. Please any feedback to: Harald.van.Breederode@Oracle.com 29