Traditional Two-Tier Client/Server
The late 1980s saw the rise of two-tier client/server applications. In this configuration,
PCs acted as clients accessing a separate database server over a network. The
client ran both the GUI and the application logic, giving rise to the term fat clients.
The database server processed SQL statements and returned the requested results
back to the clients. While database servers were relatively simple to develop using
visual tools, client/server systems were difficult to deploy and maintain??”they
required fairly high-bandwidth networks and the installation and regular upgrading
of specific client software on every user??™s PC.
Figure 9-1 illustrates the two-tier architecture.
Architectures for OLTP | 207
Stored Procedures
Oracle7 introduced stored procedures written in PL/SQL, Oracle??™s proprietary language
for writing application logic. These procedures are stored in the database and
executed by clients issuing remote procedure calls (RPCs) as opposed to executing
SQL statements. Instead of issuing multiple SQL calls, occasionally with intermediate
logic to accomplish a task, the client issues one procedure call, passing in the
required parameters.
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