Moving to a newer release.
WHY TO UPGRADE
Security fixes Performance improvements Features Support ending on old versions
WHAT TO ESTABLISH FIRST
Whether your applications support the target version.
WHAT COMMONLY BREAKS
Removed features Stricter default behaviour Changed reserved words Different default character sets or collations Authentication method changes
WHY AUTHENTICATION CHANGES CATCH PEOPLE
Older clients cannot connect to newer defaults.
WHAT TO DO
Test every application against the new version first.
WHAT THE PROCESS IS
Read the release notes for every version you skip Test on a copy Run the upgrade checking tool, where provided Back up completely Upgrade Run the upgrade routine Verify
WHY READING EVERY INTERMEDIATE VERSION MATTERS
Breaking changes accumulate across releases.
WHAT TO NEVER DO
Skip several major versions in one step, unless supported Upgrade without a tested route back
WHAT THE ROUTE BACK IS
The backup, and the old version still installed or available.
WHAT TO VERIFY AFTERWARDS
Applications connect Queries return the same results Performance has not regressed
WHY PERFORMANCE SPECIFICALLY
Optimiser changes can alter plans, occasionally for the worse.
