1. Primary Database and Standby Database Should be same. (But 11g Onwards it supports Heteregenous Data Guard Configurations. Example : We can imeplement Oracle Data Guard between Oracle Linux server 6.2 (x86_64) and Microsoft Windows 2008 Server R2 (x64)
2. Oracle Database version should be same in source and target
3. No additional license required for Oracle Data Guard to install.
Oracle GoldenGate :
1. Operating System in Primary Database and Standby Database need not be same.
2. Primary Database and Standby Database need not be same. (Including Database Software).
3. Oracle GoldenGate Software Licence required in Source and Target Databases.