Databases Reference
In-Depth Information
by global clients. The GDS configuration acts as a single virtual server supporting one
or more common workloads as global services. Optimal workload resource utilization
is managed across the replicated Oracle databases. Key components in the architecture
include Active Data Guard, Data Guard Broker, and GoldenGate.
GDS Oracle Databases that are managed by a common administrator are said to be in
the same GDS pool. All Oracle databases providing the same global service(s) must be
in the same pool.
GDS regions are typically geographically bounded. The Global Service Manager acts as
a regional listener that clients use to connect to the global services they need. The Global
Service Manager also provides service-level load balancing, failover, and centralized
management of services. The metadata repository that stores GDS configuration and
global service data is called the GDS catalog.
Data Transport Using Database Features
The previous sections focused on sharing data between distributed databases when the
data is “live” by propagating changes among databases. Oracle also provides ways to
speed up the distribution of data through the export and import of tablespaces, tables,
or entire databases.
Transportable tablespaces
are a way to speed up the distribution of complete tablespaces
between multiple databases while the tablespaces are not active. They were introduced
with Oracle8
i
Enterprise Edition to rapidly copy and distribute tablespaces among da‐
tabase instances. Previously, tablespaces needed to be exported from the source database
and imported at the target (or unloaded and loaded). Transportable tablespaces enable
copies to be moved simply through the use of file transfer commands such as
ftp
.
Transportable tablespaces have long been popular in data warehousing for copying from
data warehouses to data marts. They've also been useful when used as backup copies
for rapid point-in-time tablespace recovery.
Before you copy and move a copy of a tablespace, make sure the tablespace is read-only
to avoid inadvertently changing it. Data dictionary information needs to be exported
from the source prior to transfer, and then imported at the target. Cross-platform back‐
ups and restores using transportable tablespaces can be performed where Oracle Da‐
tabase 12
c
is deployed, somewhat simplifying data movement process across platforms.
Where transportable tables are used, they automatically identify the tablespaces used
by the tables. In fact, you can use this feature to copy tables, partitions, or subpartitions
from one database to another. When moving transportable tablespaces and tables
among current Oracle Database releases, you must use the Oracle Data Pump (instead
of the legacy import and export features of the Oracle database used prior to Oracle
Database 10
g
).
