MS SQL temporal table update failure
<p>I cant find anything to explain why when calling a SP that does a insert or update depending on if record already exists on a  temporal table i get </p>

<blockquote>
  <p>Data modification failed on system-versioned table
  'MYDB.dbo.TemporalExample' because transaction time was earlier than
  period start time for affected records.</p>
</blockquote>

<p>what dose that mean ? It only seems to happen some of the time , i wonder if its because im running multi threaded code and azure sql just doesn't like mutual connections to the same table when its a temporal one ? Im going though entity framework (latest version) but i doubt that's the issue</p>

<p>my sp just this</p>

<pre>

create PROCEDURE mysp 
    @ID bigint,
    @a FLOAT,
    @b NVARCHAR(10),
    @c  DECIMAL(19, 4)
AS
    SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED    

    SET NOCOUNT ON    

    BEGIN TRY

        IF EXISTS ( SELECT TOP 1 
                        Id 
                    FROM 
                        my_Temporal_Table WITH (NOLOCK) 
                    WHERE 
                        id = @ID 
                        AND a = @a
                        AND b = @b)
            BEGIN

                UPDATE 
                    my_Temporal_Table
                SET
                    Id = @ID,
                    a = @a,
                    b = @b
                    c = @c
                    DateModified =  GETUTCDATE()
                WHERE 
                    Id = @Id

            END
        ELSE    
            BEGIN

                INSERT INTO 
                    my_Temporal_Table
                        (Id, a, b, c, DateModified)
                VALUES 
                        (@ID, @a, @b, @c , GETUTCDATE())        
            END

    END TRY
    BEGIN CATCH
        DECLARE @ErrorMessage   NVARCHAR(4000),
                @ErrorSeverity  INT,
                @ErrorState     INT

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

        -- Use RAISERROR inside the CATCH block to return error
        -- information about the original error that caused
        -- execution to jump to the CATCH block.
        RAISERROR (@ErrorMessage, -- Message text.
                   @ErrorSeverity, -- Severity.
                   @ErrorState -- State.
                   )

    END CATCH

</pre>

<p><strong>Update</strong>
my temporal table creation script :</p>

<pre>

    CREATE TABLE [Temporal](
    [TemporalId] [bigint] IDENTITY(1,1) NOT NULL,
    [Payment] [decimal](19, 4) NOT NULL,
    [DateModified] [datetime2](7) NOT NULL,
    [SysStartTime] [datetime2](7) GENERATED ALWAYS AS ROW START NOT NULL,
    [SysEndTime] [datetime2](7) GENERATED ALWAYS AS ROW END NOT NULL,
    CONSTRAINT [TemporalId] PRIMARY KEY CLUSTERED ([TemporalId] ASC)
        WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON),
    PERIOD FOR SYSTEM_TIME ([SysStartTime], [SysEndTime])
    )WITH(
    SYSTEM_VERSIONING = ON ( HISTORY_TABLE = [Car2].[TemporalHistory] )
    )

</pre>

<p>can someone explain why i might see this issue, what it means and more importantly how i can fix it ?</p>

<p>thanks</p>