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Application Continuity
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- 2. 2ni.com About National Instruments Founded:1976 Corporate Headquarters: Austin, Texas Industry: Test and Measurement Our Mission: We equip engineers and scientists with systems that accelerate productivity, innovation, and discovery. Revenue: $1.24 billion in 2014 Global Operations: Approximately 7,100 employees; operations in almost 50 countries IT Development Centers: • Austin, Texas • Debrecen, Hungary • Penang, Malaysia • San José, Costa Rica • Shanghai, China
- 3. 3ni.com About Sean Braymen Title:Senior Oracle Database Administrator Education: Kansas State University Work History: • National Instruments for 14 Years • Prior to becoming a DBA: Manufacturing IT; eCommerce Advisors • 4 Years as a DBA Family: Wife and 5 Year Old Daughter Hobbies: Distance Running; Travel
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- 5. 5ni.com What is ApplicationContinuity • Application Continuity is a feature that attempts to mask database session outages by recovering the in-flight work for request submitted to the database. • Application Continuity attempts to replay the transactional and nontransactional work that makes up a database request. When replay is successful, the outage appears to the end user as if the execution was slightly delayed.
- 6. 6ni.com Key Concepts forApplication Continuity • Database Request: Unit of work submitted from the application, typically SQL, PL/SQL, RPC calls • Recoverable Error: Error that arises due to an external system failure, independent of the application • Commit Outcome: Outcome of the last transaction • Mutable Functions: Functions that change their results each time they are executed • Session State Consistency: Describes how the application changes the nontransactional state during a database request
- 7. 7ni.com What is TransactionGuard? Transaction Guard is: • A tool that provides a reliable commit outcome for the last transaction after errors • An API available for JDBC Thin, C/C++ (OCI/OCCI), and ODP.NET • Used by Application Continuity for at-most-once execution • Can be used independently of Application Continuity Without Transaction Guard, retry can cause logical corruption
- 8. 8ni.com How Transaction GuardWorks *LTXID: Logical Transaction ID
- 9. 9ni.com Transaction in Action:WithoutApplication Continuity 1. Work Request 2. DB Calls 3. DB Error / Shutdown 4. Application Errors
- 10. 10ni.com What Did theEnd User See? • Application received an “ORA-03113: end-of-file communication channel” • Application error handling can vary • Blank screen; generic error page; cryptic error message; etc • Developing a solution inside the application is difficult and expensive • Database outages can cause: • In-flight work to be lost, leaving users in doubt • Users to restart applications and re-entering data, leading to duplication of requests • Additional failures that result in prolonged outages
- 11. 11ni.com Transaction in Action:WithApplication Continuity 1. Work Request 2. DB Calls 3. Error / Shutdown 4. Replay 5. Response
- 12. 12ni.com What Did theEnd User See? • Application completed it work without any displayed errors • Application took slightly longer to accomplish the task than normal
- 13. 13ni.com Processing Phases ofApplication Continuity Normal Run Time Reconnect Replay • Start the database request • Builds proxy objects • Holds the original calls with validation • Manages queues • Ensure that the request has replay enabled • Handles timeouts • Creates a new connection • Validates the target database • Uses Transaction Guard to enforce last commit • Replays held calls • Continues replay, if user-visible results match base on validations • Continues the request • Throws the original exception if replay is unsuccessful
- 14. 14ni.com Requirements for ApplicationContinuity • Oracle Database 12c • Oracle Database 12c for SQL*Plus Connections • Oracle JDBC Driver 12.1.0.2 or later • Oracle Universal Connection Pool (UCP) o oracle.jdbc.replay.OracleDataSourceImpl – PooledConnection interface o Supported by many including: IBM WebSphere, Apache Tomcat and Red Hat JBoss • WebLogic Server 12c • Resource Needs • Memory: The JDBC replay driver requires more memory because the calls are retained until the end of the database request • CPU: The JDBC replay driver uses additional CPU for building proxy objects, managing queues and garbage collection o Overhead may be reduced for database platforms with current SPARC chips
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- 17. 17ni.com Configuration for Non-WebLogic •Configure the datasource in the properties file or provider • replay datasource=oracle.jdbc.replay.OracleDataSourceImpl • Configure the Datasource Definition • disableWASConnectionPooling = true connectionCachingEnabled=true connectionCacheName=<your_cache_name> removeExistingOracleConnectionPoolIfExists = true URL =<JDBC Connect String>
- 18. 18ni.com Configuring Database ServicesforApplication Continuity Example: srvctl add service –d <database_name –s <service_name> -failovertype TRANSACTION -commit_outcome TRUE -failoverretry # -failoverdelay # -retention_timeout # -replay_initation_timeout # Mandatory Settings Optional Settings
- 19. 19ni.com UsingApplication Continuity • SupportedOperations • SQL, PL/SQL, and JDBC RPC o SELECT o ALTER SESSION o DML o DDL o SAVEPOINT / ROLLBACK • Transaction Models o Local, Parallel, Remote, Distributed and Embedded PL/SQL • Mutable Functions • Required Transaction Guard • Works with Active Data Guard
- 20. 20ni.com Mutable Objects andApplication Continuity • SYSDATE / SYSTIMESTAMP • GRANT KEEP DATE TIME TO <user>; • SEQUENCES • GRANT KEEP SEQUENCES ON <sequence_name> TO <user> • CREATE SEQUENCE <sequence_name> KEEP; • ALTER SEQUENCE <sequence_name> KEEP;
- 21. 21ni.com Restrictions for ApplicationContinuity • Unsupported Operations • Default Database Services • JDBC Concrete Classes o Old Java classes: oracle.sql.* o New interfaces: oracle.jdbc.* • XA Transactions • 3rd Party Statement Cache • Replay is not supported for Active Data Guard with read/write database links
- 22. 22ni.com Restrictions for ApplicationContinuity • Transaction Types with Risks • UTL_FILE Operations • Email or notifications using DBMS_ALERT, UTL_MAIL, UTL_SMTP • Web Service calls (UTL_HTTP) • Autonomous Transactions • Transactions over database link
- 23. 23ni.com Administration • Stopping asession without replay • alter system kill session ‘sid, serial#, @inst’ noreplay; • alter system disconnect session ‘sid, serial#, @inst’ noreplay; • Stopping a service • srvctl stop service –d <database_name> -s <service_name> -noreplay • Stopping an instance • srvctl stop instance –d <database_name> -i <instance> -noreplay
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