ORACLE: GoldenGate vs DataGuard

Oracle MAA (Maximum Availability Architecture is Oracle’s best practices blueprint based
on proven Oracle high availability technologies, expert recommendations and customer
experiences. The goal of MAA is to achieve optimal high availability for Oracle customers
at the lowest cost and complexity.
RAC, DataGuard, Flashback, ASM, RMAN, GoldenGate are tools that are part of MAA
architecture.
The configuration of Oracle GoldenGate / Data Guard has the purpose of synchronizing
data between two or more systems .
The basic features of the two products may look similar but takes GoldenGate uses
replication while dataguard not.
Oracle Data Guard and GoldenGate involving at least two systems where transactional data
from one database is required to be moved to another database. The purpose of the
replication of data can be disaster recovery, migration of data or preparation of a
secondary system.
Data Guard is best for disaster recovery and data protection problems, GoldenGate is a
more flexible heterogeneous replication mechanism and is also able to transform the data
while it is being replicated.
GoldenGate is excellent in the following areas and it fit very well with your existing
Data Guard solution:

• Data Guard is an Oracle specific technology while GoldenGate support
  heterogeneous database systems including all the major RDBMS as DB2,
  Sybase, MySql .
• Data Guard supports active-passive replication. One of the database is the
  primary database and the other one is in an inactive Data Guard mode.
  GoldenGate supports an active-active replication mode and allows both
  systems to work simultaneously while maintaining the data integrity.
• GoldenGate allows transformation of the data, with conflict management
  while it is being replicated between both database systems.
• GoldenGate allows replication across platform. Data can be extracted from a
  Unix platform and replicated to an Oracle database running on platform
  Windows.
• GoldenGate has many case of utilization. The use of flat files for data transportation and
  the support of heterogeneous systems makes the technology so very interesting
  Below are some use cases of GoldenGate replication:
• Zero Downtime Upgrade/Migration : you may want to setup an
  exact replica of your database for upgrade or migration, keep the data in
  sync till the last moment.
• High Availability : your business applications cannot have downtime, so
  you want to have two databases up and running at the same time to
  support those applications.
• Real Time BI : For your data warehouse requirements.
• Query or Report : You can lighten the database production performing
  all the operations of reporting or database query on another database