Session_08 - Database Security Database Links Database...

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Database Security
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Database Links
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Database Links Provide a way to logically link two different databases Previously a complex extraction program would have been written pass data from one database to another A Link is a pointer from one database to another (not from one table to another table in the same database)
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Database Links Provide location transparence They let you treat tables in two different database as thought they were in the same database The location and complex naming structures are concealed and you have a virtual database of all database that are linked (location of data is transparent)
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Simple Client/server Client Server DB
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Database Link (Server to Server Connection) Client Server DB Server DB Database Link
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DB ORDERS Database ORDERS_TAB Table DB Database Link CUSTOMERS Database CUSTOMERS_TAB Table
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Create Database Link create database link OUR_CUSTOMER connect to ORDERS identified by C_Code using ‘connect string’ e.g., ‘(description=(address=(protocol=tcp) (host=customer.our.company.com) (port=1521)) (connect_data=(service_name=customer)))’
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tnsnames OR = (DESCRIPTION= (ADDRESS_LIST = (ADDRESS = (PROTOCOL=TCP) (HOST= customer.our.company.com) (PORT=1521)) ) (CONNECT DATA = (SERVER_NAME = customer) ) )
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Connect Strings Can be found in tnsnames.ora or provided as connect strings Consists of: protocol, host name, database name, i.e., address=protocol+host+port protocol=tcp host=customer.our.company.com port=1521 service_name=customer
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Create Database Link Using tnsnames create database link OUR_CUSTOMER connect to ORDERS identified by C_Code using ‘OR’
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Hierarchy Chart US Centerville Fairfax Atlanta XYZPRO XYZPRO XYZPRO XYZCORP Domain Naming Convention: xyz.us.centerville; xyz.us.fairfax; xyz.us.atlanta Database Naming Convention: xyzpro.xyz.us.centerville; xyzpro.xyz.us.fairfax; xyzpro.xyz.us.atlanta
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Finding Global Names col name format a22 col value format a36 select name, value from v$parameter where name = 'global_name'; select * from Global_Name; GLOBAL_NAME ------------------------------------------- XYZPRO.XYZ.US.CENTERVILLE
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Types of Database Links Public: many users can connect to the same remote database through one link Private: single user; owner of private link or subprogram within the same schema may use (more secure) Global: many users to many databases seamlessly; centralized and simple database link management Uses Oracle Names (need to migrate to directory server)
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This note was uploaded on 12/23/2009 for the course DBST dbst 668 taught by Professor Yelena - ta during the Spring '09 term at MD University College.

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Session_08 - Database Security Database Links Database...

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