Database Reference
In-Depth Information
respectively. A partition for the West Coast could contain rows from
states such as CA (California) and OR (Oregon).
Hash partitions divide up partition values evenly based on hash val-
ues calculated on a column value or values in each row of a table.
Composite partitions are partitions containing other subset partitions
or subpartitions. There are two types of composite partitions:
A range partition containing hash subpartitions or a
range-hash
partition
.
A range partition containing list subpartitions or a
range-list partition
.
Other than the huge impact of parallel processing of multiple partitions
concurrently, or of pruning out of unwanted partitions, various tricks can
be performed with partitions. Various types of operations can be performed
on partitions individually, affecting only small physical parts of very large
tables. Individual partitions can be:
Added to a group of partitions, dropped from a set of partitions, or
truncated as a single partition within a set of partitions. Thus we can
change a small part of a very large table. Efficient!
Split into new multiple partitions or merged together.
Renamed, moved, or exchanged (swap one partition for another).
3.5.3
Replication
Traditionally, replication is intended to link databases distributed over large
geographic areas where data is not only shared but specific chunks of data
are exclusive to specific sites. In general, replication occurs in two forms as
either master-to-slave replication or master-to-master replication, as shown
in Figure 3.11.
Master-to-slave replication implies that data travels in only one direc-
tion, and master-to-master replication has data traveling in both directions,
between two databases. There can be multiple databases in a set of repli-
cated databases. More specifically, using Oracle Replication software, in a
master-to-slave database environment, the slave database consists of a data-
base comprised solely of materialized views. Effectively, master-to-slave rep-
lication does not exist for the Oracle Replication option.
