The Undo-Transaction cmdlet rolls back the active transaction. When you roll back a transaction, the changes made by the commands in the transaction are discarded and the data is restored to its original form.

If the transaction includes multiple subscribers, an Undo-Transaction command rolls back the entire transaction for all subscribers.

By default, transactions are rolled back automatically if any command in the transaction generates an error. However, transactions can be started with a different rollback preference and you can use this cmdlet to roll back the active transaction at any time.

The Undo-Transaction cmdlet is one of a set of cmdlets that support the transactions feature in Windows PowerShell. For more information, see about_Transactions.

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-WhatIf

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The input type is the type of the objects that you can pipe to the cmdlet. The return type is the type of the objects that the cmdlet returns.

You cannot roll back a transaction that has been committed.

You cannot roll back any transaction other than the active transaction. To roll back a different, independent transaction, you must first commit or roll back the active transaction.

Rolling back the transaction ends the transaction. To use a transaction again, you must start a new transaction.

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C:\PS>undo-transaction

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This command rolls back the current (active) transaction.

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C:\PS>cd hkcu:\software PS HKCU:\Software> start-transaction PS HKCU:\Software> new-item MyCompany -usetransaction PS HKCU:\Software> undo-transaction

Description

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This command starts a transaction and then rolls it back. As a result, no changes are made to the registry.

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C:\PS>cd hkcu:\software PS HKCU:\Software> start-transaction PS HKCU:\Software> new-item MyCompany -usetransaction PS HKCU:\Software> get-transaction RollbackPreference SubscriberCount Status ------------------ --------------- ----- Error 1 Active PS HKCU:\Software> start-transaction PS HKCU:\Software> get-transaction RollbackPreference SubscriberCount Status ------------------ --------------- ----- Error 2 Active PS HKCU:\Software> undo-transaction PS HKCU:\Software> get-transaction RollbackPreference SubscriberCount Status ------------------ --------------- ----- Error 0 RolledBack

Description

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This example demonstrates that when any subscriber rolls back a transaction, the entire transaction is rolled back for all subscribers.

The first command changes the location to the HKCU:\Software registry key.

The second command starts a transaction.

The third command uses the New-Item cmdlet to create a new registry key. The command uses the UseTransaction parameter to include the change in the transaction.

The fourth command uses the Get-Transaction cmdlet to get the active transaction. Notice that the status is Active and the subscriber count is 1.

The fifth command uses the Start-Transaction command again. Typically,

starting a transaction while another transaction is in progress occurs when a script used by the main transaction includes its own complete transaction. (This example is done interactively so that you can examine it in stages.)

When you enter a Start-Transaction command while another transaction is in progress, the commands join the existing transaction as a new "subscriber" and the subscriber count is incremented.

The sixth command uses the Get-Transaction cmdlet to get the active transaction. Notice that the subscriber count is now 2.

The seventh command uses the Undo-Transaction cmdlet to roll back the transaction. This command does not return any objects.

The final command is a Get-Transaction command that gets the active (or in this case, the most recently active) transaction. The results show that the transaction is rolled back, and that the subscriber count is 0, showing that the transaction was rolled back for all subscribers.

Concepts