An 'undefined' page is any page that has been linked to from within Confluence, but that does not yet exist.

Undefined Page Linked From
ZCB (for Amazon S3) Purchase & Payment Verification Errors Page: User Guide - Yearly Plan ZCB (Google Cloud) - English (Zmanda Cloud Backup 4.9)
_System_Requirements Page: ユーザーガイド- Amazon - 日本語 (Zmanda Cloud Backup 4.9)