Problem description

The Upgrading Jira Data Center with zero downtime user guide has reference to Installer/Manual node upgrade steps:

• Upgrading Jira Data Center (installer)
• Upgrading Jira Data Center (manual)

These guides contain some general steps that are redundant for ZDU, for example, they request you to rebuild the index at Post-upgrade steps on the first node > Step 4. Rebuild index. This might lead to confusion that nodes need to be re-indexed as a part of ZDU steps.

Suggestion

1. Update Upgrading Jira Data Center (installer) Post-upgrade steps on the first node > Step 4. Rebuild index chapter with info note "Omit this step if you're upgrading your Data Center with zero downtime." (see Before you begin > Step 3: Stop the cluster for example).
2. Same change for Upgrading Jira Data Center (manual).
3. Update Zero downtime upgrade FAQs section Reindexing with additional question/answer:

   Q: Does Zero Downtime Upgrade requires manual reindexing as a mandatory step
   A: No, it is not mandatory to re-build the index during ZDU. If required, you could run a re-index after the upgrade during the suitable maintenance window.
   (optional) We could add a reference to Zero downtime upgrades for Jira Data Center applications where it is said that "Upgrading with ZDU does not require re-indexing and the state of the index after ZDU should be the same as before ZDU."