As I am an operational DBA, I take exception to the idea of expendable support DBAs.
It is all very well to be a project DBA who can list their acomplishments in their LinkedIn profile. I know it is a very good feeling to have achieved something at the end of the project. And it is very comfortable to get into the flow of problem solving and to be able to work on something without interruption.
As I noted in my comments on Don’t Multitask: Your Brain Will Thank You, my job as an operational DBA is built around interruptions. I am doing a good job when nothing untoward is happening, when the graphs are boring, and all of the alarms are silent.
As for being expendable, I would disagree because very few DBAs want to be operational DBAs. They want to have that accomplishment of having solved a very difficult, and possibly writing an insightful blog post or article or giving a presentation about it. And I, as an operational DBA, am very appreciative of this valuable corpus of work. But the reluctance of others to be in operational work makes me a Linchpin. It is about doing work no one else wants to do, and doing it well despite the lack of recognition and prestige.
When I started my IT career (sometime after the end of the last Ice Age), I was very reluctant to become a maintaince programmer, and to work in operations support. I was dragged kicking and screaming into those roles because they were part of my programming apprenticeship.
And I was glad that I was forced to do so. It took me years to appreciate the valuable skills I picked up then. I think these skills are a quick appreciation of the ways that other people express themselves in writing code and documentation, and ways of dealing with very difficult people who demand the impossible yesterday.
So, I am glad that I am an expendable support DBA. The work is very frustrating, unrewarding, and very few people can do it well (even if they wanted to). I think that being an operational DBA helped me to passed the OCM exams because I had to make quick decisions in the face of ignorance and tight time constraints.