The new tool is built, the team is trained, and the date is set. Then the data move turns out to be a Friday-evening improvisation: someone exports a sheet, someone else edits it "just one more time," and on Monday two versions of the truth exist.
This article is for an operations lead who is about to switch a team from spreadsheets to a new system. It covers only the switch weekend: what to freeze, what to check, what the hours look like and when to go back. How to choose and build the tool is covered in our guide to moving from a spreadsheet to a small internal tool in 30 days.
Why a weekend, and why a plan
Spreadsheets are edited all day by many people. A copy taken on Friday at noon is already out of date by Friday at four. The only way to get a clean copy is to stop the editing for a defined window. A weekend is usually the cheapest window, because fewer people are working and an overrun does not stop a shift.
A plan matters because during the switch nobody thinks clearly. People are tired, questions arrive from three directions, and every decision that was not made earlier gets made in a hurry.
One week before: what must be ready
- A rehearsal with a copy of the real data. Run the whole import once on a test copy and write down how long it took and what broke. The rehearsal duration is your best estimate for the real run, and you should add a margin of at least half again.
- A named person for each role. One person runs the import, one checks the results, one answers user questions, and one decides on go or rollback. The decider should not be the person doing the import.
- A list of every spreadsheet in scope, including the personal copies people keep on desktops. If a sheet is not on the list, it will keep living after the switch.
- A one-paragraph message to users that says when the sheets stop accepting changes, when the new tool opens, and where to ask for help.
The write freeze
Before any copy is taken, writing into the spreadsheets must stop. Be concrete about it.
- Announce the freeze time a week ahead and repeat it the day before.
- At the freeze time, set the files to read-only in the shared drive, or move them to a folder where only the import owner has write access.
- Note the freeze time in the plan and in the file names, for example "orders_frozen_friday_1800".
- Agree on what happens to work that arrives during the weekend. A paper list or a shared inbox is enough, as long as someone enters it into the new tool afterwards.
Do not rely on a request such as "please do not edit." A technical lock is the only freeze that holds.
An hour-by-hour plan
The times below are an example for a team that stops work on Friday evening. Scale them to the duration you measured in the rehearsal.
| When | Step | Owner |
|---|---|---|
| Fri 18:00 | Freeze: sheets set to read-only, final copy saved | Import owner |
| Fri 18:30 | Record baseline numbers: row counts per sheet, totals of key columns | Checker |
| Fri 19:00 | Run the import into the production system | Import owner |
| Fri 21:00 | Compare imported counts and totals with the baseline | Checker |
| Sat 09:00 | Open the tool to two experienced users for spot checks on real records | Support person |
| Sat 13:00 | Go or rollback decision, based on the conditions below | Decider |
| Sat 14:00 | Fix small issues found in spot checks, or start the rollback | Import owner |
| Sun 10:00 | Second check of counts and a short run of the most common daily tasks | Checker |
| Sun 16:00 | Final confirmation and message to users | Decider |
| Mon 07:30 | Support person available, list of known issues visible to all | Support person |
Leave a gap of a few hours between steps. The plan should survive one step taking twice as long.
Checksums that prove the copy is complete
You do not need special software. Three kinds of checks catch most problems:
- Row counts. Each sheet has a number of rows; the corresponding table in the new tool should have the same number, minus any rows you decided on purpose not to import.
- Column totals. For columns with amounts or quantities, sum them in the sheet and in the new tool. A difference of even one unit means something was cut, rounded or duplicated.
- Spot checks by hand. Pick ten records, including the oldest, the newest and a few with unusual values such as long text or special characters, and compare them field by field.
Write the baseline numbers down before the import starts. Numbers recorded afterwards tend to be adjusted to match.
The rollback condition
Rollback is not a failure; it is the reason you can switch with confidence. Write the condition down before the weekend, in one or two sentences, and name the person who decides. For example:
- Counts or totals do not match, and the cause is not found and fixed by the Saturday decision time.
- A core daily task cannot be completed in the new tool on real records.
- Data is visibly wrong in a way users would act on, such as customers attached to the wrong orders.
Rolling back means the spreadsheets become writable again, the new tool is closed to users, and the message to the team says when the next attempt will be. Because the sheets were only frozen and never altered, this takes minutes rather than hours. That is also the reason not to delete or "clean up" the originals during the weekend.
After the switch
Keep the old spreadsheets read-only for at least the first week, and in an archive folder for longer. Users will ask "what did the old sheet say?" and you want a calm answer. Log every difference users report and decide for each one whether it is a defect in the import or a deliberate change.
After a week of normal use, archive the sheets, remove the shortcuts and tell the team that the old files are no longer the source. If you are thinking about the longer period that follows, our guide to the first 30 days after launching a new internal tool continues from here.
Common mistakes
- Copying before freezing. The copy is stale the moment someone edits.
- Skipping the rehearsal. The real run then becomes the first run.
- Having the importer also decide on rollback. Sunk effort bends judgment.
- Cleaning up data during the switch. Clean up before, or after; never at the same time as moving it.
- Deleting the originals on Sunday. You lose the rollback and the reference.
What to do this week
List every spreadsheet in scope, run one rehearsal import on a copy, and write the rollback condition on one page with the name of the decider. Then fill in the hour-by-hour table with your own times.
Sources
- Our related articles linked above.
- The weekend structure, checks and rollback conditions are a general working approach, not a standard; all times shown are illustrative and should be adapted to the rehearsal results of your own migration.