Job Collisions

What it does

Every morning the instance gets slow for twenty minutes, and nobody can say why. Forty-six scheduled jobs start at the same instant.

This tells you which ones, and when.

Why the obvious check gives the wrong answer

Group the scheduled jobs list by start time and you get a number. On the instance this was built against, that number is 164 jobs at 08:00.

It is wrong. It counts daily jobs alongside weekly ones, monthly ones and one-offs, and those never actually run at the same moment. The real busiest slot holds 46.

Getting that right means considering the cadence, the time, the day of the week and the day of the month together. A list view groups by one field.

The screen shows both numbers side by side, so you can see the difference rather than take our word for it.

The trap underneath it

A job's start time is stored as an instant and shown to you in your own time zone:

the stored value 1970-01-01 04:00:00 (UTC) what you see 20:00:00 (your zone)

Group on what is displayed and two administrators in different time zones get different collision groups for the same instance. This groups on the instant, and shows both clocks on every slot.

What the measurement said

Active scheduled jobs - 597 With a fixed clock time - 236 Start at the same instant as at least one other - 180 Busiest single slot - 46 jobs, every day

What it will not do

It cannot change a schedule. There is no write path in this application at all - not disabled, not behind a flag.

It cannot run or cancel a job.

It ships no scheduled job of its own, which would be a peculiar thing for this product to add to the pile. There is a test that fails if one ever appears.

It will not tell you a slot is too busy. Forty jobs at midnight may be perfectly fine if they are all small. Whether a collision matters depends on what those jobs do, and that judgment stays with you.

It stores nothing. No tables ship with it, so an uninstall cannot leave residue.

Where it stops

It reads at most 3,000 active jobs and says so plainly when it stops early. Jobs with no fixed clock time - on-demand and periodic ones - cannot collide on one; they are counted and named on their own screen rather than quietly skipped, because a job the report never looked at is not a job the report cleared.

Not the same as Scheduled Job Health

That one tells you what has quietly stopped running. This one tells you what runs all at once. They answer different questions and neither replaces the other.