Lately I have been getting quite a few inquiries on database migrations asking me about migration approaches, best practices, and tooling. Some of the reasons why companies are looking at migrations are because of staffing issues, scalability and security concerns, and cost-saving strategies. Migrations have always been complex, time consuming, and expensive, because each DBMS has proprietary data structures, data types, and SQL extensions. Once you choose a DBMS, you get locked into its platform, often creating a challenge when looking to migrate. Some companies told me that it took them more than a year to migrate some large and complex applications, which is not surprising. Although, tools and services have helped with migrations in the past, they have not been comprehensive and automated, which would make the process simple. Since, I'm an IT manager in the retail sector in my opinion I would say, “We did not want to spend a million dollars on tools and services just to save a million dollars on our database platform; it just didn’t make sense.”
The good news is that there is a new option that has recently emerged and has been gaining ground. Enter the “database compatibility layer,” which changes the way migrations are done. IBM DB2 9.7 for Linux, UNIX, and Windows offers out-of-the-box compatibility for Oracle’s PL/SQL and Sybase ASE, which allows many applications to run against DB2 without any application code changes. Although the database compatibility layer does not offer 100% compatibility today, based on customer feedback from more than two dozen interviews that I have conducted this year, one can usually expect 90% or more compatibility, requiring only minor code changes. This is huge, which makes migrations simpler, taking only days and weeks as opposed to months and years. IBM jointly developed the database compatibility layer technology with vendors EnterpriseDB (for Oracle compatibility) and ANTs (for Sybase ASE compatibility), who also offer their own database migration solutions.
The database compatibility layer finally opens up the door to more migrations, reducing risk and making them cost effective. I estimate that so far, some 300 companies have migrated their databases using the database compatibility layer, and this is likely to become the standard approach for database migrations in the future.
I would love to hear feedback on database migration experiences using the compatibility layer or other approaches -- things that have worked for you and things that did not. Also, are you looking to migrate anytime soon or holding back because of the risk involved?