by Burleson Consulting
The Data Warehouse Development Life Cycle
SQL*Net For Oracle Distributed Data Warehouses
You can use database links to allow applications to point to other
databases without altering the application code. For data
warehousing applications, you can replicate a table on another
machine and establish links to enable the application to point
transparently to the new box containing the replicated table.
To see the links for a database, query the Oracle dictionary, as
SELECT DISTINCT db_link FROM
Keep in mind that SQL*Net bypasses all operating system connections
when it connects to a database. All externally identified user
accounts (that is, accounts without an Oracle password) will not be
allowed in SQL*Net transactions unless the init.ora parameter is
changed. The identified externally clause (OPS$) in Oracle version 6
allows the operating system to manage passwords, but because SQL*Net
bypasses the operating system, impostor accounts can be created from
other platforms. The result is that security can be bypassed.
Consequently, Oracle now recommends forbidding externally identified
accounts when using distributed connections, and the OPS$ features
is seldom used in Oracle7 or Oracle8.
It is interesting to note that Oracle will allow you to create
accounts with an OPS$ prefix. Therefore, the operating system can
manage its passwords, while you also have passwords within Oracle.
For example, assume the following user definition:
CREATE USER ops$scott IDENTIFIED
Assuming that Scott has logged onto the operating system, Scott
could enter SQL*Plus either with or without a password, as follows:
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