These sections describe compatibility, upgrading, downgrading, and installation topics for Oracle Database 12c Release 2 (12.2).
2.1.1 Oracle REST Data Services (ORDS)
JDK7 is the minimum Java version for Oracle REST Data Services (ORDS).
2.1.2 Core Dump ORA-00600  Error Encountered After Database Upgrade
A core dump
ORA-00600  error is encountered after the database is upgraded to Oracle Database 12c Release 2 (12.2) and then downgraded back to its original release (reference Bug 20898997).
Always apply the patch for this bug before upgrading the database to Oracle Database 12c Release 2 (12.2).
2.1.3 Downgrading Oracle Database 12c Release 2 (12.2) to Oracle Database 11g Release 2 (18.104.22.168) Results in Errors When Running utlrp.sql
If SQLJ types are present when downgrading from Oracle Database 12c Release 2 (12.2) to Oracle Database 11g Release 2 (22.214.171.124), then the following
ORA-00600 error can occur when running
utlrp.sql to recompile invalid objects after running
catrelod.sql (reference Bug 16230705):
ORA-00600: internal error code, arguments: 
Apply the patch for this bug and recompile the type using the
ALTER TYPE COMPILE statement.
2.1.4 Select Product Languages Screen Missing in Oracle Client
Starting with Oracle Database 12c Release 2 (126.96.36.199), the Select Product Languages screen has been removed and Oracle Universal Installer installs all supported language files irrespective of the operating system locale (reference Bug 18223148).