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Managing Transactions

At the end of this module you will be able to:

Configure transactions using the console

Monitor transactions using the console

Module 9

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1. Configuring and Monitoring Transactions Configuring Transactions Monitoring Transactions The Transaction Log

Road Map

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What Is a Transaction?

A transaction is a mechanism to handle groups ofoperations as though they were one.

Either all operations in a transaction occur or none atall.

Operations involved in a transaction might rely onmultiple servers and databases.

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ACID Properties of a Transaction

A transaction is formally defined by the set of propertiesknown by the acronym ACID.

Atomicity : A transaction is done or undone completely. In theevent of a failure, all operations and procedures are undone,and all data rolls back to its previous state.

Consistency : A transaction transforms a system from oneconsistent state to another consistent state.

Isolation : Each transaction occurs independently of othertransactions occurring at the same time.

Durability : Completed transactions remain permanent, evenduring system failure.

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Transaction Management

Application 1

MessagingServer

SQL serverDatabase

(Resource)

PointBaseDatabase

(Resource)

Manages

Transactions

End-to-EndTransaction Manager

WebLogicServer

Resource Manager

Resource Manager

Resource Manager

JTA

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Transferring Without Transactions

Successful transfer (A)

Unsuccessful transfer (accounts are left in an inconsistent state)(B)

$1000+$100$1100

$500-$100

$400

2) Deposit: $100

1) Withdraw: $100

Transfer: $100From: Acct 1To: Acct 2

ATM Bank

Account 1

Account 2

$1000

$500-$100

$4001) Withdraw: $100

Transfer: $100From: Acct 1To: Acct 2

ATM Bank

Account 1

Account 2FailedDeposit

A

B

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Successful Transfer with Transactions

Changes within a transaction are buffered. (A)

If a transfer is successful, changes are committed (made permanent). (B)

Transfer: $100From: Acct 1To: Acct 2

ATM Bank

Transaction Started by Bank $500-$100

$4001) Withdraw: $100 Account 1

Account 2$1000+$100$1100

2) Deposit: $100

Transaction Started by Bank

$1100

$400Commit

TransferSuccessful

ATM Bank Account 1

Account 2Commit

A

B

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Changes within a transaction are buffered. (A)

If a problem occurs, the transaction is rolled back to the previousconsistent state. (B)

Transfer: $100From: Acct 1To: Acct 2

ATM Bank

Transaction Started by Bank

$1000

$500

-$100$400

1) Withdraw: $100 Account 1

Account 2FailedDeposit

Transaction Started by Bank

$1000

$500Rollback

Errormessage

ATM Bank Account 1

Account 2Rollback

Unsuccessful Transfer with Transactions

A

B

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Types of Transactions

A local transaction deals with a single resourcemanager. They use the non-Extended Architecture(non-XA) interface between WebLogic Server andresource managers.

A distributed transaction coordinates or spans multipleresource managers.Global transactions can deal with multiple resourcemanagers. They use the Extended Architecture (XA)interface between WebLogic Server and resourcemanagers. You need to create non-XA or XA resources for local

transactions. However, for global transactions, you only needto create XA resources.

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The Two-Phase Commit Protocol

The Two-Phase Commit (2PC) protocol uses two stepsto commit changes within a distributed transaction. Phase 1 asks RMs to prepare to make the changes Phase 2 asks RMs to commit and make the changes

permanent, or to roll back the entire transactionA global transaction ID (XID ) is used to track allchanges associated with a distributed transaction.

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Extended Architecture Protocol

The Extended Architecture (XA) protocol: Is the interface used between WLS and RMs Implements the 2PC protocol Allows programs to control RMs that are involved in

distributed transactions

Client TransactionManager

RM1

RM2

XA

XA

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A transaction manager coordinates multiple resource managers.

The 2PC protocol is used to coordinate the transaction.

The XA protocol implements 2PC.

Transaction and Resource Managers

Transaction Context started by Transaction Manager

TransactionManager

ResourceManager

ResourceManager

ResourceManager

Database

Printer

Another App

Application

XA

XA

XA

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Successful Two-Phase Commit

Application

TLOG

TransactionManager

ResourceManager

ResourceManager

ResourceManager

Database

Printer

Another App

Applicationpre-commit

ready

TransactionManager

ResourceManager

ResourceManager

ResourceManager

Database

Printer

Another App

commit

committed

Phase 1Phase 2

TLOG

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Unsuccessful Two-Phase Commit

pre-commit

abort

notready

ready

prepare/abort

ready/committed

notready

rolledback

ResourceManagerResourceManager

ResourceManager

Database

Printer

Another App

ResourceManager

ResourceManagerResourceManager

Database

Printer Another

App

Application

TLOG

TransactionManager

Application

TransactionManager

Phase 1Phase 2

TLOG

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Java Transaction API (JTA)

WLS uses JTA to implement and manage transactions.WLS JTA provides the following support: It creates a unique transaction identifier ( XID ).

It supports an optional transaction name. It tracks objects involved in transactions. It notifies databases of transactions. It orchestrates 2PC using XA.

It executes rollbacks. It executes automatic recovery procedures when failure. It manages time-outs.

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Configuring Transactions

2

1

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Each server has a transaction log that storesinformation about committed transactions coordinated by the server that may not have been completed. WebLogic Server uses the transaction log when recovering

from system crashes or network failures.You cannot directly view the transaction log as therecords are in a binary format.

T-log files must be migrated if migrating to a newmachine.

Configuring the Transaction Log

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Configuring the Transaction Log

.tlog files are stored in the default persistent storefor the server.

Directory represents the path name to the file systemdirectory where the file store maintains its data files.

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JTA Configuration Options

Field Description

Timeout Seconds Specifies the time in which a transaction willtimeout, if uncommitted

Abandon Timeout Seconds Specifies the maximum time that a transactionmanager will persist in attempting to complete atransaction during the second phase of thetransaction

Before Completion IterationLimit

Specifies the maximum number of cycles thatthe transaction manager will perform thebeforeCompletion() synchronizationcallback for this WebLogic Server domain

Max Transactions Specifies the maximum number of

simultaneous in-progress transactions allowedon a server in the domain

Max Unique Name Statistics Specifies the maximum number of uniquetransaction names for which statistics will bemaintained

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JTA Configuration Options

Field Description

Checkpoint Interval Seconds Specifies the interval at which the transactionmanager creates a new transaction log file andchecks all old transaction log files to see if theyare ready to be deleted

Forget Heuristics Specifies whether the transaction manager willautomatically perform an XAResource forget() operation for heuristic transaction completions

Unregister Resource GracePeriod

Specifies the grace period, in seconds, that thetransaction manager waits for transactionsinvolving the resource to complete beforeunregistering a resource

Security Interoperability Mode Specifies the security mode to use for XA calls ininter-domain transactions

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Creating XA Resources

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Creating Non- XA Resources

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Creating Non -XA Resources

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Logging Last Resource

You can configure a JDBC data source to enable the LoggingLast Resource (LLR) transaction optimization, which: Enables one non-XA resource to participate in a global transaction Has improved performance and the same ACID guarantee as XA

The LLR optimization improves performance by: Removing the need for an XA JDBC driver to connect to the database.XA JDBC drivers are typically inefficient compared to non-XA JDBCdrivers

Reducing the number of processing steps to complete the transaction,which also reduces network traffic and I/O

Removing the need for XA processing at the database level (if thedatabase is the one non-XA resource)

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Transacted Messaging

A JMS client can use JTA to participate in a distributedtransaction.

Alternatively, a JMS client can demarcate transactionslocal to the JMS Session through a transacted session.

Participation in a transaction is optional.

All messages arriveat destination

Begin Transact ion 1

C o m m i t

Begin Transact ion 2

C o m m i t

Producer Consumer

Messages are removedfrom destination

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Inter-Domain Transactions

WebLogic Server supports global transactions acrossdomains on different versions of WebLogic Server.

To enable WebLogic Server domains for inter-domaintransactions:

Enable trust between the different domains Ensure that each contributing XA resource has a unique

name Ensure that only one of the participating resources in the

distributed transaction can emulate the two-phase commitor XA protocol

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Enable Trust Among Different Domains

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Monitoring Transactions by Resource

For a particular resource, the console providesmonitoring of transactional outcomes: Number of transactions attempted Number of commits/rollbacks

Number of heuristic outcomes

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Monitoring Transactions

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Section Review

Configuring transactions

Monitoring transactions

Logging transactions

In this section we discussed:

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Exercise

In these labs you will work with monitoring DataSources.

Ask the instructor for any clarification.The instructor willdetermine the stop time.

Data Sources and Transactions

Lab Exercise

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Module Review

Configuring transactions using the console

Monitoring transactions in WebLogic Server

In this module we discussed: