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Start-Transaction

Tue Jan 29, 2019 10:20 pm

NAME Start-Transaction



SYNOPSIS

Starts a transaction.





SYNTAX

Start-Transaction [-Confirm] [-Independent] [-RollbackPreference {Error | TerminatingError | Never}] [-Timeout <Int32>] [-WhatIf]

[<CommonParameters>]





DESCRIPTION

The Start-Transaction cmdlet starts a transaction, which is a series of commands that are managed as a unit. A transaction can be completed, or

committed. Alternatively, it can be completely undone, or rolled back, so that any data changed by the transaction is restored to its original

state. Because the commands in a transaction are managed as a unit, either all commands are committed or all commands are rolled back.



By default, if any command in the transaction generates an error, transactions are rolled back automatically. You can use the RollbackPreference

parameter to change this behavior.



The cmdlets used in a transaction must be designed to support transactions. Cmdlets that support transactions have a UseTransaction parameter. To

perform transactions in a provider, the provider must support transactions. The Windows PowerShell Registry provider in Windows Vista and later

versions of the Windows operating system supports transactions. You can also use the Microsoft.PowerShell.Commands.Management.TransactedString

class to include expressions in transactions on any version of the Windows system that supports Windows PowerShell. Other Windows PowerShell

providers can also support transactions.



Only one transaction can be active at a time. If you start a new, independent transaction while a transaction is in progress, the new transaction

becomes the active transaction, and you must commit or roll back the new transaction before you make any changes to the original transaction.

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

about_Transactions.





PARAMETERS

-Confirm [<SwitchParameter>]

Prompts you for confirmation before running the cmdlet.



Required? false

Position? named

Default value False

Accept pipeline input? False

Accept wildcard characters? false



-Independent [<SwitchParameter>]

Indicates that this cmdlet starts a transaction that is independent of any transactions in progress. By default, if you use Start-Transaction

while another transaction is in progress, a new subscriber is added to the transaction in progress. This parameter has an effect only when a

transaction is already in progress in the session.



By default, if you use Start-Transaction while a transaction is in progress, the existing transaction object is reused and the subscriber

count is incremented. The effect is much like joining the original transaction. An Undo-Transaction command rolls back the whole the

transaction. To complete the transaction, you must enter a Complete-Transaction command for each subscriber. Because most transactions that

are in progress at the same time are related, the default is sufficient for most uses.



If you specify the Independent parameter, this cmdlet creates a new transaction that can be completed or undone without affecting the original

transaction. However, because only one transaction can be active at a time, you must complete or roll back the new transaction before resuming

work on the original transaction.



Required? false

Position? named

Default value False

Accept pipeline input? False

Accept wildcard characters? false



-RollbackPreference <RollbackSeverity>

Specifies the conditions under which a transaction is automatically rolled back. The acceptable values for this parameter are:



- Error. The transaction is rolled back automatically if a terminating or non-terminating error occurs. - TerminatingError. The transaction

is rolled back automatically if a terminating error occurs. - Never. The transaction is never rolled back automatically.



The default value is Error.



Required? false

Position? named

Default value None

Accept pipeline input? False

Accept wildcard characters? false



-Timeout <Int32>

Specifies the maximum time, in minutes, that the transaction is active. When the time-out expires, the transaction is automatically rolled

back.



By default, there is no time-out for transactions that are started at the command line. When transactions are started by a script, the default

time-out is 30 minutes.



Required? false

Position? named

Default value None

Accept pipeline input? False

Accept wildcard characters? false



-WhatIf [<SwitchParameter>]

Shows what would happen if the cmdlet runs. The cmdlet is not run.



Required? false

Position? named

Default value False

Accept pipeline input? False

Accept wildcard characters? false



<CommonParameters>

This cmdlet supports the common parameters: Verbose, Debug,

ErrorAction, ErrorVariable, WarningAction, WarningVariable,

OutBuffer, PipelineVariable, and OutVariable. For more information, see

about_CommonParameters (http://go.microsoft.com/fwlink/?LinkID=113216).



INPUTS

None

You cannot pipe input to this cmdlet.





OUTPUTS

None

This cmdlet does not generate any output.





NOTES









Example 1: Start and roll back a transaction



PS C:\\>cd hkcu:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item "ContosoCompany" -UseTransaction

PS HKCU:\\software> New-ItemProperty "ContosoCompany" -Name "MyKey" -Value 123 -UseTransaction

PS HKCU:\\software> Undo-Transaction



These commands start and then roll back a transaction. Because the transaction is rolled back, no changes are made to the registry.

Example 2: Start and complete a transaction



PS C:\\>cd hkcu:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item "ContosoCompany" -UseTransaction

PS HKCU:\\software> New-ItemProperty "ContosoCompany" -Name "MyKey" -Value 123 -UseTransaction

PS HKCU:\\software> Complete-Transaction



These commands start and then complete a transaction. No changes are made to the registry until the Complete-Transaction command is used.

Example 3: Use different rollback preferences



PS C:\\>cd HKCU:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item -Path "NoPath" -Name "ContosoCompany" -UseTransaction

PS HKCU:\\software> New-Item -Path . -Name "ContosoCompany" -UseTransaction

PS HKCU:\\software> Start-Transaction -RollbackPreference never

PS HKCU:\\software> New-Item -Path "NoPath" -Name "ContosoCompany" -UseTransaction

PS HKCU:\\software> New-Item -Path . -Name "ContosoCompany" -UseTransaction



# Start-Transaction (-rollbackpreference error)



PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item -Path "NoPath" -Name "ContosoCompany" -UseTransaction

New-Item : The registry key at the specified path does not exist.

At line:1 char:9

+ new-item <<<< -Path NoPath -Name ContosoCompany -UseTransaction



PS HKCU:\\software> New-Item -Path . -Name "Contoso" -UseTransaction



New-Item : Cannot use transaction. The transaction has been rolled back or has timed out.

At line:1 char:9

+ new-item <<<< -Path . -Name ContosoCompany -UseTransaction



# Start-Transaction (-rollbackpreference never)



PS HKCU:\\software> Start-Transaction -RollbackPreference never

PS HKCU:\\software> New-Item -Path "NoPath" -Name "ContosoCompany" -UseTransaction



New-Item : The registry key at the specified path does not exist.

At line:1 char:9

+ new-item <<<< -Path NoPath -Name "ContosoCompany" -UseTransaction

PS HKCU:\\software> New-Item -Path . -Name "ContosoCompany" -UseTransaction



Hive: HKEY_CURRENT_USER\\Software

SKC VC Name Property

--- -- ---- --------

0 0 ContosoCompany {}

PS HKCU:\\Software> Complete-Transaction



# Succeeds



This example demonstrates the effect of changing the RollbackPreference parameter value.



In the first set of commands, Start-Transaction does not use RollbackPreference . As a result, the default value (Error) is used. When an error

occurs in a transaction command, that is, the specified path does not exist, the transaction is automatically rolled back.



In the second set of commands, Start-Transaction uses RollbackPreference with a value of Never. As a result, when an error occurs in a transaction

command, the transaction is still active and can be completed successfully.



Because most transactions must be performed without error, the default value of RollbackPreference is typically preferred.

Example 4: Use this cmdlet while a transaction is in progress



PS C:\\>cd HKCU:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item "ContosoCompany" -UseTransaction

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> Get-Transaction

PS HKCU:\\software> New-Item "ContosoCompany2" -UseTransaction

PS HKCU:\\software> Complete-Transaction

PS HKCU:\\software> Complete-Transaction

PS HKCU:\\Software> Get-Transaction

RollbackPreference SubscriberCount Status

------------------ --------------- ------

Error 2 Active



This example shows the effect of using Start-Transaction while a transaction is in progress. The effect is much like joining the transaction in

progress.



Although this is a simplified command, this scenario frequently occurs when the transaction involves running a script that includes a complete

transaction.



The first Start-Transaction command starts the transaction. The first New-Item command is part of the transaction.



The second Start-Transaction command adds a new subscriber to the transaction. The Get-Transaction command now returns a transaction with a

subscriber count of 2. The second New-Item command is part of the same transaction.



No changes are made to the registry until the whole transaction is completed. To complete the transaction, you must enter two Complete-Transaction

commands, one for each subscriber. If you were to roll back the transaction at any point, all the transaction would be rolled back for both

subscribers.

Example 5: Start an independent transaction while one is in progress



PS C:\\>cd HKCU:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item "ContosoCompany" -UseTransaction

PS HKCU:\\software> Start-Transaction -Independent

PS HKCU:\\software> Get-Transaction

PS HKCU:\\software> Undo-Transaction

PS HKCU:\\software> New-ItemProperty -Path "ContosoCompany" -Name "MyKey" -Value 123 -UseTransaction

PS HKCU:\\software> Complete-Transaction

PS HKCU:\\software> dir contoso*

PS HKCU:\\Software> Get-Transaction



RollbackPreference SubscriberCount Status

------------------ --------------- ------

Error 1 Active

PS HKCU:\\software> Undo-Transaction

PS HKCU:\\software> New-ItemProperty -Path "ContosoCompany" -Name "MyKey" -Value 123 -UseTransaction

MyKey

-----

123

PS HKCU:\\software> Complete-Transaction

PS HKCU:\\software> dir contoso*

Hive: HKEY_CURRENT_USER\\Software

SKC VC Name Property

--- -- ---- --------

0 1 MyCompany {MyKey}



This example shows the effect of using the Independent parameter of Start-Transaction to start a transaction while another transaction is in

progress. In this case, the new transaction is rolled back without affecting the original transaction.



Although the transactions are logically independent, because only one transaction can be active at a time, you must roll back or commit the newest

transaction before resuming work on the original transaction.



The first set of commands starts a transaction. The New-Item command is part of the first transaction.



In the second set of commands, the Start-Transaction command uses the Independent parameter. The Get-Transaction command that follows shows the

transaction object for the active transaction, which is the newest one. The subscriber count is equal to 1, that shows that the transactions are

unrelated.



When the active transaction is rolled back by using an Undo-Transaction command, the original transaction becomes active again.



The New-ItemProperty command, which is part of the original transaction, finishes without error, and the original transaction can be completed by

using the Complete-Transaction command. As a result, the registry is changed.

Example 6: Run commands that are not part of a transaction



PS C:\\>cd hkcu:\\software

PS HKCU:\\software> Start-Transaction

PS HKCU:\\software> New-Item "ContosoCompany1" -UseTransaction

PS HKCU:\\software> New-Item "ContosoCompany2"

PS HKCU:\\software> New-Item "ContosoCompany3" -UseTransaction

PS HKCU:\\software> dir contoso*

PS HKCU:\\software> Complete-Transaction

PS HKCU:\\software> dir contoso*

PS HKCU:\\Software> dir contoso*



Hive: HKEY_CURRENT_USER\\Software

SKC VC Name Property

--- -- ---- --------

0 0 ContosoCompany2 {}



PS HKCU:\\Software> Complete-Transaction

PS HKCU:\\Software> dir contoso*



Hive: HKEY_CURRENT_USER\\Software

SKC VC Name Property

--- -- ---- --------

0 0 ContosoCompany1 {}

0 0 ContosoCompany2 {}

0 0 ContosoCompany3 {}



This example demonstrates that commands that are submitted while a transaction is in progress can be included in the transaction or not included.

Only commands that use the UseTransaction parameter are part of the transaction.



The first and third New-Item commands use the UseTransaction parameter. These commands are part of the transaction. Because the second New-Item

command does not use the UseTransaction parameter, it is not part of the transaction.



The first dir command shows the effect. The second New-Item command is completed immediately, but the first and third New-Item commands are not

effective until the transaction is committed.



The Complete-Transaction command commits the transaction. As a result, the second dir command shows that all of the new items are added to the

registry.

Example 7: Roll back a transaction that does not finish in a specified time



PS C:\\>Start-Transaction -Timeout 2



# Wait two minutes...



PS C:\\>Get-Transaction

PS C:\\>New-Item HKCU:\\Software\\ContosoCompany -UseTransaction

PS C:\\>Start-Transaction -Timeout 2



# Wait two minutes...



PS C:\\>> Get-Transaction



RollbackPreference SubscriberCount Status

------------------ --------------- -----------

Error 1 RolledBack



PS C:\\>New-Item HKCU:\\Software\\ContosoCompany -UseTransaction



New-Item : Cannot use transaction. The transaction has been rolled back or has timed out.

At line:1 char:9

+ new-item <<<< MyCompany -UseTransaction



This command uses the Timeout parameter of Start-Transaction to start a transaction that must be completed within two minutes. If the transaction

is not finished when the time-out expires, it is rolled back automatically.



When the time-out expires, you are not notified, but the Status property of the transaction object is set to RolledBack and commands that use the

UseTransaction parameter fail.



RELATED LINKS

Online Version: http://go.microsoft.com/fwlink/?LinkId=821640

Complete-Transaction

Get-Transaction

Undo-Transaction

Use-Transaction