Payday disaster
A firm replaces its old payroll system with a new one. On the day, the old system is switched off and the new one is switched on.
On payday, 300 workers are paid the wrong amount. The old system is gone. There is no copy. It takes two weeks to fix.
What should the firm have done? Test properly. Choose a safer way to switch. And plan a way back.
Key words
| Word | What it means | Example |
|---|---|---|
| Test environment | A safe copy of the system, used only for tests. It is not the real system that people use (the live system). | A computer used only for tests |
| Reproducible | Gives the same result every time you run it the same way. | The same test, the same answer |
| Parallel running | Run the old and the new systems together for a time. | Both pay the staff, and we compare |
| Phased roll-out | Introduce the new system one part at a time. | One department a month |
| Direct change-over | Switch off the old system and switch on the new one at once. | At midnight on Sunday |
| Pilot | Try the new system with a small group first. | One office of 10 people |
| Rollback | Going back to the old, working version. | Restore last night's backup |
| Backup | A copy of data or a system, kept in case of a problem. | A nightly copy |
| Legacy system | An older system that the organisation still uses. | An old stock program |
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Quick check: payday disaster
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Configure the new system
Before use, a new system must be set up (configured) to fit the organisation. Two points are very important.
Working with the legacy systems. The new system must share data with the old ones that stay.
Keeping the service running. Customers and staff must still be able to work while the change happens.
Test fully, in a safe place
Test the new system before anybody depends on it. Use a test environment: a copy of the live system (the real system people use). It has the same kind of hardware and software. Mistakes do no harm there.
Tests must be reproducible. If you run the same test twice in the same way, you get the same result. Then you can trust it, and you can find and fix problems.
Test in the right place
| Where | Good or bad? | Why |
|---|---|---|
| The live system | Bad | A mistake affects real customers |
| A test environment that matches live | Good | Safe, and results are close to real |
| A test environment with different software | Poor | A pass may not mean a pass in live |
| Tests written down and repeatable | Good | Anybody can run them again and get the same answer |
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Quick check: testing
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