SQLServerCentral Article

Optimizing DTS Data Loads

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In this article, we will discuss how to optimize loading a

sample file into SQL Server using DTS. 

There are a number of tasks that you can use to load the data including

the Transform Data Task, the Bulk Insert Task and the Data Driven Query

Task.  In this article, we’ll cover

performance differences between all the tasks and how to increase your

performance on some of the slower tasks.

To quantify the data load procedure,

we’re loading a flat file that contains a mailing list with more than 15,000

records and 30 columns.  The same concepts

that we discuss in this article would work among any type of data load

generally.  The first way we’re

going to load the data from the flat file, is by using the transform data task

in a simple transformation as shown below:

By default, DTS will automatically map the transformation for

you between each column as shown below.  Each column is mapped

based on column name and ordinal position automatically.

Each connecting line represents a COM object that has to be created to transform the

data.  There is quite a bit of

overhead to do this and in our case, this is an unnecessary step since

everything maps perfectly.  

When loading a lot of data, make sure that you temporarily drop indexes

on the destination table.  If you don't drop the

indexes on large tables, you will notice a significant performance degregation. When

loading a small amount of data (50,000 or less is my rule of thumb), you will

not receive a benefit from this. 

After running this transformation that we just created we noted the time

of 5 seconds.

Custom scripting (written in VBScript or

JScript usually) will enhance the transformation logic but also slow you down. We ran the same transformation using VBScript and

noticed it took 13 seconds.  The

same transformation written in JScript took 19 seconds.  The reason for this is DTS is no longer

using the optimized COM objects that it ships with.  Instead it uses your uncompiled code

that you create.  Any added logic

you place on DTS like this will slow it down.  For example, if we place some VBScript

logic in each field to make it upper case then our time of 13 seconds jumps to

24 seconds.  If you need to perform

custom logic like this, DTS in SQL Server 2000 ships with a number of predefined

COM objects that can perform this action.

When running the Import/Export Wizard I noticed that no

matter what type of transformation we selected (VBScript or Copy Columns), our

transformation time was almost 50% of the previous transformation.  After saving a package and going to the

transformation tab as shown below we can see why.   DTS is optimizing itself to use

only one COM object to transform all the data.  If you’re writing a package in the

Designer you can do the same thing. 

Simply delete all the transformation lines and then create a new

transformation that uses all the source columns as the source and all the

destination columns for the destination. 

The result should look like this:

By doing this, our basic transformation now takes 3 seconds

and our VBScript transformation takes 8. 

You can also see in the below chart that the Bulk Insert task was our

fastest since no transformations occur in the task.  The Bulk Insert task only took DTS 2

seconds to execute.  The below chart

covers the results and the time it took for the records to transform among for

all transformations.

Result 1

Basic

Result 2

Sharing COM

Transformation

Result 3

Sharing COM Transformation and

VB

Result 4

VB

For Each Transformations

Result 5

Jscript for Each

Transformation

Result 6

Bulk

Insert

 As you can see, the Bulk Insert Task is much faster for

loading data.  However the

limitations may outweigh any benefits from speed.  For example, to use the Bulk Insert

Task, the columns’ schema on the source must exactly match the columns on the

destination other than length.  A

great alternative with decent speed is going to be the Transform Data Task when

using one COM object.  Other options

like Fast Load under the options tab can further increase performance of your

data load since it bypasses triggers.

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