SAVE TRANSACTION (Transact-SQL)

Artykuł
12/03/2008

Sets a savepoint within a transaction.

Syntax

SAVE { TRAN | TRANSACTION } { savepoint_name | @savepoint_variable }
[ ; ]

Arguments

savepoint_name
Is the name assigned to the savepoint. Savepoint names must conform to the rules for identifiers, but are limited to 32 characters.

@savepoint_variable
Is the name of a user-defined variable containing a valid savepoint name. The variable must be declared with a char, varchar, nchar, or nvarchar data type. More than 32 characters can be passed to the variable, but only the first 32 characters will be used.

Remarks

A user can set a savepoint, or marker, within a transaction. The savepoint defines a location to which a transaction can return if part of the transaction is conditionally canceled. If a transaction is rolled back to a savepoint, it must proceed to completion with more Transact-SQL statements if needed and a COMMIT TRANSACTION statement, or it must be canceled altogether by rolling the transaction back to its beginning. To cancel an entire transaction, use the form ROLLBACK TRANSACTION transaction_name. All the statements or procedures of the transaction are undone.

Duplicate savepoint names are allowed in a transaction, but a ROLLBACK TRANSACTION statement that specifies the savepoint name will only roll the transaction back to the most recent SAVE TRANSACTION using that name.

SAVE TRANSACTION is not supported in distributed transactions started either explicitly with BEGIN DISTRIBUTED TRANSACTION or escalated from a local transaction.

Important

When a transaction begins, resources used during the transaction are held until the completion of the transaction (namely, locks). When part of a transaction is rolled back to a savepoint, resources continue to be held until the completion of the transaction or a rollback of the complete transaction.

Permissions

Requires membership in the public role.

Examples

This example illustrates using a transaction savepoint to roll back only the modifications made by a stored procedure if an active transaction is started before the stored procedure is executed.

USE AdventureWorks;
GO
IF EXISTS (SELECT name FROM sys.objects
           WHERE name = N'SaveTranExample')
    DROP PROCEDURE SaveTranExample;
GO
CREATE PROCEDURE SaveTranExample
    @InputCandidateID INT
AS
    -- Detect if the procedure was called
    -- from an active transaction and save
    -- that for later use.
    -- In the procedure, @TranCounter = 0
    -- means there was no active transaction
    -- and the procedure started one.
    -- @TranCounter > 0 means an active
    -- transaction was started before the 
    -- procedure was called.
    DECLARE @TranCounter INT;
    SET @TranCounter = @@TRANCOUNT;
    IF @TranCounter > 0
        -- Procedure called when there is
        -- an active transaction.
        -- Create a savepoint to be able
        -- to roll back only the work done
        -- in the procedure if there is an
        -- error.
        SAVE TRANSACTION ProcedureSave;
    ELSE
        -- Procedure must start its own
        -- transaction.
        BEGIN TRANSACTION;
    -- Modify database.
    BEGIN TRY
        DELETE HumanResources.JobCandidate
            WHERE JobCandidateID = @InputCandidateID;
        -- Get here if no errors; must commit
        -- any transaction started in the
        -- procedure, but not commit a transaction
        -- started before the transaction was called.
        IF @TranCounter = 0
            -- @TranCounter = 0 means no transaction was
            -- started before the procedure was called.
            -- The procedure must commit the transaction
            -- it started.
            COMMIT TRANSACTION;
    END TRY
    BEGIN CATCH
        -- An error occurred; must determine
        -- which type of rollback will roll
        -- back only the work done in the
        -- procedure.
        IF @TranCounter = 0
            -- Transaction started in procedure.
            -- Roll back complete transaction.
            ROLLBACK TRANSACTION;
        ELSE
            -- Transaction started before procedure
            -- called, do not roll back modifications
            -- made before the procedure was called.
            IF XACT_STATE() <> -1
                -- If the transaction is still valid, just
                -- roll back to the savepoint set at the
                -- start of the stored procedure.
                ROLLBACK TRANSACTION ProcedureSave;
                -- If the transaction is uncommitable, a
                -- rollback to the savepoint is not allowed
                -- because the savepoint rollback writes to
                -- the log. Just return to the caller, which
                -- should roll back the outer transaction.

        -- After the appropriate rollback, echo error
        -- information to the caller.
        DECLARE @ErrorMessage NVARCHAR(4000);
        DECLARE @ErrorSeverity INT;
        DECLARE @ErrorState INT;

        SELECT @ErrorMessage = ERROR_MESSAGE();
        SELECT @ErrorSeverity = ERROR_SEVERITY();
        SELECT @ErrorState = ERROR_STATE();

        RAISERROR (@ErrorMessage, -- Message text.
                   @ErrorSeverity, -- Severity.
                   @ErrorState -- State.
                   );
    END CATCH
GO

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SAVE TRANSACTION (Transact-SQL)

Syntax

Arguments

Remarks

Permissions

Examples

See Also

Reference

Other Resources

Help and Information

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