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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

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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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Application Continuity

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What is Application Continuity

• 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.

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Key Concepts for Application 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

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What is Transaction Guard?

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

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How Transaction Guard Works

*LTXID: Logical Transaction ID

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Transaction in Action: Without Application Continuity

1. Work Request

2. DB Calls

3. DB Error / Shutdown

4. Application Errors

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What Did the End 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

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Transaction in Action: With Application Continuity

1. Work Request

2. DB Calls

3. Error / Shutdown4. Replay

5. Response

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What Did the End User See?

• Application completed it work without any displayed

errors

• Application took slightly longer to accomplish the task

than normal

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Processing Phases of Application 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

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Requirements for Application Continuity

• 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 Tomcatand 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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Configuring Application Continuity

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WebLogic Server 12c

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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>

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Configuring Database Services for Application 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

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Using Application Continuity

• Supported Operations

• 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

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Mutable Objects and Application 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;

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Restrictions for Application Continuity

• 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

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Restrictions for Application Continuity

• 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

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Administration

• Stopping a session 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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Demo

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