Moving from a legacy CMS into AEM requires the organization and management of a lot of moving parts; each of which must be rooted in your current needs, while keeping future strategic goals in mind. One of the most crucial steps is data migration, because the content needs to be moved into, and made acceptable, for the new system. A complication often occurs because of the time gap between content migration completion and site launch, when a data clean up is necessary. However, for most organizations, authors are not likely to be able to stop creating content for any length of time. Therefore, it is critical to define a content cutoff strategy to ensure that all of the content created in this interim is migrated over to the new system, yet allows the least interruption to modifying and generating new content.
Delta migration is a process that was created by Blue Acorn iCi experts in response to a recent client migration project to address the long duration of a typical content freeze. Using the Content Scanner tool, also developed in-house, our team created a way to minimize the burden on both the client’s authors, as well as our own consultants.
There are a few terms defined below that will help in understanding the concept and benefits of a delta migration:
The content freeze is the time period when authors cannot make any changes to content, including creating, updating, or deleting – within the legacy CMS or AEM system. It normally occurs after a migration, when the data must be cleaned.
A double posting is when authors must post in both the legacy CMS and the AEM environment. In this case, content authors will be responsible for making sure the legacy and AEM systems are completely in sync with any changes they’ve made (ie creating, updating, or deleting content). It occurs during a migration when two systems are active (the legacy and the new AEM systems).
Post migration content clean up:
Once content is migrated over to AEM, there may be some content that requires clean up by the authors. A clean up is often necessary because data from an unstructured legacy system may not correlate directly into AEM, or there can be unsupported HTML from the legacy system.
What is Delta Migration?
The Need for Efficiency
Clients want to spend the least time possible in either an extended content freeze, or a double posting window, because both place constraints and stress on their authors. Yet, in AEM’s OOTB state, both are necessary in order to get started on content cleaning. That is why utilizing the concept of a delta content migration is the most efficient process to move legacy content into an AEM system.
Delta content is any content that is added, deleted, or modified during the defined delta period. It is identified by flagging a system modification date or tagging pages manually.
Delta content migration:
Delta content migration is a process that eliminates the need for a long content freeze or double posting period. It recognizes content that has been created, edited, or deleted between the initial extract and the second extract at the close of the period, done when the data migration is completed.
A short freeze is still necessary when delta content is extracted from the legacy system and provided to the vendor to add to the target system, but it is a considerably shorter window.
Delta migration can be achieved in one of two ways:
- Taking delta content directly from the legacy system – in this case authors must track modified pages
- Identifying delta content by relying on a system generated field (ex: date field) to distinguish what has been authored within the delta timeframe
Advantages of a delta migration include:
- Less time in the content freeze period
- Less time in the double posting period
- More time for content validation and clean up
- The ability to receive content into the target system in incremental pieces
As with any process, there is a downside. When working with a delta migration, the content that has been deleted in the delta period will have to be manually tracked and deleted as part of the final content clean up. AEM does not provide a way to compare data to identify which pages are missing (i.e. have been deleted) so a subtract comparison is needed.
A Practical Example
Imagine a site with over 20,000 pages of content that has 50 contributing authors across the globe. When it is all migrated into AEM, out of those 20,000 pages, there are 2,000 pages that require manual clean up (remember, manual clean up is often necessary to match some of a legacy system’s data to the AEM system). It’s estimated that a dedicated team will need one month to clean up those 2,000 pages.
In addition, 4,000 pages have had modifications made to them during the migration period, in-turn creating an additional 1,000 out of 4,000 pages that need manual clean up attention after the migration.
This organization cannot afford an extended content freeze that will keep those 1,000 new pages from being published on time. However, because the team needs a month dedicated to AEM content clean up, without a delta migration, a freeze would be necessary. A delta migration would allow them to continue to bring in new pages (the 1,000 in this example) or make modifications to existing pages, while performing the necessary tasks associated with a content clean up.
The Bottom Line
Data migration can prove to be a long and complex process. The time and cost savings for an organization who can utilize a delta migration are immense. It gives sufficient time to clean up the content post-migration, while allowing authors to modify and create content in the system. We’d love to talk more about our delta process and how our expertise in migration can benefit you!