by Burleson Consulting
The Data Warehouse Development Life Cycle
Distributed Oracle Data Warehouses
Miscellaneous Management Tips For SQL*Net
It is possible to run two listeners simultaneously, one for version
1.0 and another listener for version 2.0. If a version 1.0 connect
string is sent, a version 1.0 listener (tcpctl) will be used.
Conversely, if a TNS connect description is sent, the version 2.0
listener (lsnrctl) will be used. A connect description is the name
of a database (such as @mydata), which maps to the tnsnames.ora on
the sending side and listener.ora on the receiving side.
It is essential to note that the functions of the ORACLE_SID and
TWO_TASK variables have changed between SQL*Net version 1 and
SQL*Net version 2. To use the MTS while you are local to the
database, you should unset the ORACLE_SID variable and set the
TWO_TASK to the SID name (EXPORT TWO_TASK=mydb). If the ORACLE_SID
is active, you will still be able to connect--although you will not
be able to take advantage of the MTS. You must change all login
scripts and ORACLE_HOME/bin/oraenv files to reflect this new
We now have three ways to establish distributed database
communications with MTS. We can choose from a shared service-name (sqlplus
/@ram2db) or a dedicated service name (sqlplus /@d_ram2db--prefixing
the SID with d_ will direct the listener to spawn a dedicated
process for your program). And, we can also use a (TWO_TASK) server
connect string (sqlplus /@t:host:sid). This latter approach will
bypass the MTS and use a dedicated process.
This is an excerpt from "High Performance
Data Warehousing", copyright 1997.
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