Which system owns the data?
If stock, price or customer information can change in two places, agree on ownership first.
Two updates can conflict
If a store changes a price and accounting sends the old value back, the problem is not just sync frequency. Ownership is unclear. Sending data more often can amplify the conflict.
Assign ownership by field
Product codes, quantities and selling prices may belong to different systems. Agree on the source, update direction and correction owner for each field.
Start with a table
Use columns for information, source, consumers and owner. Fill in five critical fields, including which record wins if a conflict occurs.