You're facing a database migration with limited downtime. How can you prioritize tasks effectively?

As an SAP-basis consultant, I conducted a comprehensive assessment for migrating an S4HANA 2020 system between data centres with minimal downtime. The client, a retail customer, required a maximum of four hours of downtime, necessitating a seamless migration strategy. I proposed using a Disaster Recovery (DR) approach, setting up a DR site for replication before bringing the system online. To mitigate potential complications, I planned to migrate the development environment first, before proceeding with quality and production landscapes. This thorough assessment included reviewing OS versions, HANA DB versions, DB size, frequency of logs generated, application version, interfaces, and third-party licenses.

To ensure a smooth project, I meticulously planned the migration after an initial assessment. Activities were split into those executable without downtime and those requiring downtime. Pre-downtime tasks included building a shell system, taking online backups, and verifying data, followed by enabling replication to the DR site followed by activities during down time. I shared this plan with all stakeholders through meetings, outlining each team's responsibilities. After obtaining consent from every team, we conducted a mock cutover to test all scenarios and verify the timings in PRD system. Additionally, a contingency plan was included to revert to the primary site if the cutover failed.

Informing stack holders is very essential, so they know the reason for it. For example if it's a banking app, all the users should be notified before one or 2 days before so they will manage their transactions accordingly

While migrating the database with low downtime, each task had its importance. We chalked out the sequence with a lot of precision in terms of data migration and reconfiguration of applications in the least possible time of downtime. On migration day, we carried forward our plan step by step, ensuring that each task was executed in the proper order. Midway, we encountered a data inconsistency issue; since we were monitoring closely, we addressed it quickly, hence resulting in minimal downtime. This migration was a success, and it was smoothly done within the duration set for it. The experience proved that ensuring proper implementation and constant monitoring is a way to secure migration that has less influence on operations.