The directory that you specify when you are prompted for ORACLE_BASE by Oracle Universal Installer is stored in the Oracle home inventory. Database Upgrade Assistant uses this value to derive the default database locations and the DIAGNOSTIC_DEST parameter. The diagnostic destination location contains all ADR directories (diagnostic files, such as the alert logs, trace files, and so on). This diagnostic destination directory is required while upgrading an earlier Oracle Database release to Oracle Database 11g release of the database. If the Oracle base directory already exists, then Oracle Database Upgrade Assistant automatically retrieves this information and populates its path. Starting with Oracle Database 11g Release 1, the initialization parameter settings for background dump (BACKGROUND_DUMP_DEST), user dump (USER_DUMP_DEST), and core dump (CORE_DUMP_DEST) destinations are replaced by the Diagnostic Destination (DIAGNOSTIC_DEST).