Here in the UK, we are due to change our timezone back to Greenwich Mean Time (GMT) from British Summer Time (BST) on 25th October. My company usually takes this evening as an opportunity for more in depth routine maintenance and software/hardware upgrades as our main application will be offline throughout this period. Due to time constraints, my senior managers were exploring ways in which they perceived that time could be saved in order to fit the required work into a much smaller time frame - one key piece of work we were scheduled to complete was the upgrade of our database and grid infrastructure to Oracle 19.8.

My managers asked me whether there would be any issues with performing this upgrade during the moment of the clock change itself because we'd gain an extra hour and would help them alleviate their time constraints. The clock change itself occurs at 02:00 BST which then becomes 01:00 GMT. Regardless of the precise moment the upgrade began, they were asking whether there would be any implications with actual, technical upgrade steps (either clusterware or database) happening at the moment of the clock change. In my ten years of being a DBA, I've always scheduled my work of this nature around such a moment "just in case" by finishing or pausing by 01:00 BST and then resuming after 01:00 GMT but I was unable to give my managers a technical reason or justification as to why work cannot carry on through this moment. I simply, albeit very strongly and as diplomatically as I could stress, said that it would most likely go against good practice and could put us on a very sticky wicket with support if we were to need their help should anything go wrong.

I'm fully aware of the SCN within the database as its internal clock but with clusterware and its interaction with networking, storage and other such things I would have thought time would have a greater importance, most certainly during such a major piece of work like an upgrade. I did raise a support question with Oracle support themselves but I think they may have misunderstood, perhaps they don't often receive such questions.

My question to you, and certainly the advice I'd like to receive, would almost not be whether this is technically possible to achieve (although I'd still very much like to know) but what your opinion would be regarding such a situation. Is it something you have performed elsewhere or do you avoid such tasks during moments like this "just in case"?

As a result of other issues, we are actually postponing this upgrade for this time and will complete it on another date so overall my point is moot for another year but I'd really like to know your thoughts, if only from a philosophical perspective!

Thanks again for all your work.

Kind regards,

Graham