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Tales from the Battle Field

This article refers to one of several problems I came across when attempting to upsize from Access 2000 to SQL Server. Hopefully, you will pick up a few tips that will save you a heap of time.

There are 3 things I will discuss:
1. Microsoft Access 2000 Upsizing Wizard
2. SQL Server 7 and 2000 DTS (Data Transformation Services)
3. SSW Upsizing PRO!

When transferring data from Access to SQL Server, most people use and recommend using SQL Server DTS because the Microsoft Upsizing Wizard does have its problems. By the end of this article, you will see that the Microsoft Upsizing Wizard has a place equal or greater than DTS in this transfer process.

Before starting you can check out these links and read this article from Microsoft http://www.microsoft.com/SQL/techinfo/migrate.htm . A plethora of articles are also at http://www.ssw.com.au/ssw/upsizingpro/frmLinks.htm BUT STOP! Don't follow those links! It will take you at least a week to understand and check all that stuff. I recommend using the Microsoft Upsizing Wizard, and SSW Upsizing PRO! which will only take 5 minutes to understand, and a few hours to implement.

Only a few days...

Let me tell you about a situation I encountered a while ago (Names changed of course). I was working for a very short-tempered man (ST for short), CEO of Backyard Accounting Corporation. He wanted his 100MB database moved to SQL Server. He told us that he just didn't have time for a long-winded conversion process. Upon further investigation I discovered that his database was stitched together by his son, Mr ST Junior - so that the company could save money.

Mr ST called me in the office and said "Can you start transfering the data? My son has heard on the newsgroups that SQL Server DTS is the way to go." I say "Fine".

Ho hum, I sit down and take a look at Mr ST's database - the usual assortment of Clients, Accounts and Invoices. Yawn. This is going to be a walk in the park.

An hour or so later I see Mr ST with my conversion schedule in hand. We go through it together:

  • Split the database (into a backend and frontend)

  • Move the data to SQL Server.

  • Link the tables

  • Test out the forms

I tell Mr ST that it shouldn't take more than a day to convert the database. He grins, and his gold teeth light up the room.

I add "Unless there are problems of course." I get that ghastly look but he says "Excellent! Begin the conversion process. I will tell my workers that they will be off-line tomorrow."

A few days later, I am sweating like a pig at 3:00am in the morning. I have given up on DTS, as it constantly gave errors that I just could not isolate. I have also discovered that it doesn't transfer the hundreds of relationships - maybe I should have made time to read through the 50+ page articles on Microsoft's esteemed web site. Mr ST is getting very upset. What can I do?

Microsoft Upsizing Wizard

I tell Mr ST that Microsoft also has an Upsizing Wizard. He sounds impressed and I decide to take that approach.

Upsizing PRO

Unfortunately there were also problems with the Microsoft Upsizing Wizard. It turns out the conversion process of a backend Access mdb to SQL server is no small task if you have a database any more complicated than Northwind (which Microsoft must have done all their testing on).

Please Give me an Explanation

Access and SQL Server talk the same language most of the time... Most of the common field types can are translated fine. For example, a "Memo" field in Access would be a "Text" field in SQL Server. Most relationships translate 1:1 from Access to SQL Server.

However, there are subtle differences between the two. The "Text" fields in Access can only be 255 characters long, whereas the equivalent data types of "Varchar" and "Nvarchar" can store 8000 and 4000 characters respectively. Another element of difference is that Access and SQL Server have different default behaviours. For example, by default, Microsoft Access disallows fields with blank strings i.e. "Allow Zero Length" = No. However, SQL Server allows such fields by default. Differences like these have to be kept in mind on the winding road to upsizing heaven.

Please give me a solution

So wouldn't it be good if there was a utility that would tell you all the things in your Access database, that are going to cause SQL Server problems. Aka cause the Microsoft Upsizing Wizard to fall over. Well there is. It is called SSW Upsizing PRO! available at www.ssw.com.au

Today I use SSW Upsizing PRO! whenever I start an upsizing job. The report it generates gives me a quick idea of how complicated this job is going to be in the first place. It incorporates the recommendations of many upsizing documents into one easy-to-use utility. It also compares your old mdb file with the newly upsized SQL Server database so that you can be assured that the conversion was accurate. Read on to find out more about making an 'upsizing' as painless as possible.

Essential Things

As much as we love the Microsoft Access 2000 Upsizing Wizard, it still has deficiencies. These range from missing constraints to complete tables being skipped without any significant warnings. SSW Upsizing PRO! highlights these problems, so you can be prepared for such issues. These problems include (but are not limited to):

  • The Microsoft Upsizing Wizard allows tables without unique constraints. Tables with this problem cannot be modified.
  • SQL Server and the Microsoft Upsizing Wizard allow spaces in table and field names (e.g. "Order Details"), but this is not a good idea.
  • Validation rules are not upsized.
  • If a unique index is set on a field, and the required property is set to "No" in Access, the Microsoft Upsizing Wizard will fail.
  • If you have created a table and then reordered the fields after you have saved it (everybody does this), the Microsoft Upsizing Wizard will often fall over.
  • Multiple Key Foreign Key Relationships on tables that map to fields of a different name will fail. (As below)

Sample relationship

  • Tables with invalid dates will be skipped without warning (SQL Server smalldatetime can only store from the years 1900 to 2079. Dates outside this range will fail.) For example, Access will allow data entry errors such as '1/1/199'.
  • Fields with multiple-key indexes cannot be upsized if the total size of the fields adds to more than 450 characters.

Running SSW Upsizing PRO!

All you need to do is to select the data .mdb file and it will give you a report on all problems that need to be fixed. For example, it will inform you of the columns with invalid dates, and how to isolate the culprit records. After upsizing, it will compare the SQL Server Database, so you can be assured that your data and all relationships have been transferred correctly.

DTS is still useful, but...

I wouldn't use DTS to upsize my data to SQL Server, because it doesn't convert relationships, and is not as robust with some data types, such as time and date fields. But it is still useful for diagnosing problems with data. For example, suppose you have a table that will not upsize with the Microsoft Upsizing Wizard. If there is a problem, it will skip the data, and sometimes the remaining table structures as well. What is really useful is that you can use DTS to find the problem by telling you the line number where it is falling over, so you can correct the erroneous data.

However, it is not useful for importing time-related data. See DTS Horror Stories for more detailed information on the example problem.

Conclusion

Sometimes you wish you had the time to build the database schema from scratch! This is not practical in the majority of cases, and this is where the SSW Upsizing PRO! fills the gap - to tell you the problems that exist in you mdb file, to make your experience with the Microsoft Upsizing Wizard as smooth as possible.

For a seamless transition from Access to SQL Server, the Developer has to use many tools to:

  • Isolate bad data (usually date data)
  • Find structural problems (the source of most errors)
  • Counter problems in the official Upsizing tools provided by Microsoft.

These tools include:

  • SSW Upsizing PRO!
  • Microsoft SQL Server DTS
  • Cutting and Pasting in Microsoft Access

With the deficiencies of DTS in mind, the Microsoft Upsizing Wizard is your best overall solution to upsizing. I recommend using the Microsoft Upsizing Wizard as your primary tool, with DTS as an ancillary tool for troubleshooting minor problems. In summary, use SSW Upsizing PRO! in conjunction with the Microsoft Upsizing Wizard for a relatively hassle-free upsizing process. Of course, Mr TW will be much happier!

Without these tools, there is a steep hill to climb, particularly when you are faced with the upsize of a large and/or complicated legacy Access database.

Adam Cogan and David Klein
December 2000