Stanford researcher Clifford Nass found in a 2009 study that:
This suggests a two-task limit on what the human brain can handle. Taking on more tasks increases the likelihood of errors, so Nass suggests what he calls the 20-minute rule. Rather than switching tasks from minute to minute, dedicate a 20-minute chunk of time to a single task, then switch to the next one.
Nass also suggests relying on e-mail less.
This is going to difficult for me as an operational DBA to do. My job revolves around interruptions all day long.
As for e-mail, I have to continually monitoring for incoming alerts. I get between 200 and 2,000 e-mails daily. Monday morning is the worse when I can wade through up to 5,000 e-mails for a bad weekend.
Fortunately, I have set up rules to route e-mails to the appropriate folders. Even then I am skimming through the subjects of the e-mails to decide which e-mails to read or delete.
We have been trying to reduce this flood of e-mails by fixing problems and tuning the metric thresholds for Cloud Control alerts.
One significant factor in managing Cloud Control alerts is to separate production from non-production targets. This means we can see production alerts more clearly without being buried among non-production problems.
If I find myself with 1,000 or more emails on a Monday morning, I just delete them all and work from the Incident Console within Cloud Control to sort out what alerts are still outstanding. Even this is fraught with difficulties because there are so many spurious alerts generated by Cloud Control especially around Grid Infrastructure. We have reported several of these as bugs to Oracle Support.
As for the limit of spending 20 minutes on a single task, this would mean that I could look at a maximum of about 20 tasks per working day. In a working year of 200 days, this means a maximum of about 4,000 tasks per year.
When I was the team leader, the DBA team of five (5) Oracle RDBMS DBAs processed about 600 work tickets per month, or 7,200 per year. This meant each DBA could process an average of about 7 tickets per day. Or about an average of one (1) ticket per hour per DBA. So, an average ticket would be about three (3) 20 minute tasks.