Consider data synchronization during transitions
December 14, 2005
By Nicholas Fortin
For readers who own an HP e3000 server and are interested in the subject of transitions, data synchronization is not talked about very much. One of the most critical topics to focus on during migration planning is the deployment strategy, especially its impact and relation to data migration and data cutover for moving to production. Sometimes you will need to use data synchronization technology to support your desired deployment strategy.
A database synchronization technology facilitates the synchronization of data from one database type to another, usually located on different platforms (making sure updates performed on one database are also performed on another database, as well as keeping the two synchronized). To use a basic example of how this would apply for IMAGE to Eloquence, you migrate an IMAGE database to Eloquence, and then keep the Eloquence database synchronized (updated) with the transactions performed on the HP e3000. Why would you want to do this? Well, I have some examples below.
First, let me go over some migration challenges or caveats related to this topic. You may need a data synchronization technology if one of the following scenarios apply to you:
1. Your databases are large and your available downtime small enough to make it impossible to migrate all your databases in the final cutover period (this is sometimes referred to as the big-bang approach). To explain, first let’s make some assumptions. We’ll assume that the databases are large enough to require a significant amount of time to migrate from one type to another (we also underline — although it’s probably implied — that when the databases are migrated, they need to be put offline so no transactions are performed in order to migrate a specific snapshot of the data).
In addition, we’ll assume that a business has a small user downtime period allowed for switching the users to the new system. These two traits combine to pose a data migration challenge because at the moment of final data cutover, before moving all users to production on the target system, the time needed to migrate the IMAGE databases surpasses the time limitations for the HP e3000 system databases to be un-accessed (i.e., database downtime). These two criteria show potential synchronization need.
In this scenario, once a snapshot of your databases is taken (using a backup, copy or an export of your databases) during the transition project, you could use a synchronization tool to keep your target database synchronized with updates continued to be performed on the HP e3000. This scenario represents unidirectional synchronization from source to target.
2. Your testing strategy requires platform parallel testing of screens and reports (and sometimes transactional programs) — testing whose results depend on the exact same data values from both source and target databases at any given time. This scenario represents unidirectional synchronization from source to target.
3. You envision a contingency backup plan to revert back to the HP e3000 after having moved into production on your target server (for a set period of time like a week or two), in the event the migrated application environment has some serious problems. You would then need a synchronization technology to keep the IMAGE databases synchronized with the target transactions. This scenario represents unidirectional synchronization from target to source.
4. You envision a deployment strategy which requires a phased deployment of portions of your applications into separate bundles migrated, tested and moved into production. In this scenario, you have the same databases (usually some of your databases) on your source and target system accessed/updated simultaneously live in production requiring that databases on both platforms be kept synchronized with minimal discrepancy delay.
Due to the importance of having data integrity between databases on different platforms, this scenario also usually implies using a two-phase-commit mechanism to ensure data is posted correctly before the application process can move on. This scenario represents bidirectional synchronization from source to target and target to source simultaneously.
In fact, for two of our currently on-going large migration projects, this topic carried so much importance that it was included in a strategies/technologies validation milestone phase occurring as the first part of the project. (This phase has the objective to make the customer feel confident in some key technologies which may not be as proven as others, or which may carry unanswered questions needed for the transition project).
There are a few synchronization technologies available which support a number of database types including TurboIMAGE, each of them carrying their own strengths and “particularities.”
Another branch of this topic is data synchronization for flat or KSAM files. Although flat files are usually small in nature, a company that has hundreds or thousands of flat files to migrate can be faced with the same challenges noted above for databases. Becasue the migration process challenges and solutions for files are different than for databases, file synchronization is out of the scope of this article. However, Speedware possesses a unique and innovative tool that can migrate and synchronize thousands of flat files efficiently, quickly and with integrity.
In summary, synchronization can:
• Help with a phased deployment for the data cut-over
• Help with 24x7 or extreme uptime server requirements
• Help to run HP e3000 and Unix systems in parallel in production
• Help for a contingency plan in case the deployment is problematic
This information just scratches the surface of this topic. If you want to find out more about data synchronization and how it would relate to your environment and particular needs, you should talk to an expert who has this knowledge.
Speedware is an HP e3000 platinum transition partner which possesses a unique expertise in this domain based on real experience. Speedware has several data synchronization software and tools available.