Oracle Evolution towards distributed databases

If we start with the hardware framework, we see that he first generation technology was characterized by vacuum tube hardware.  Languages that were developed during this period were designed to provide a handle on the generation of object code, the binary language that operated directly on the machine.  These code "assembly" languages became very popular and added to the mystique of computing by requiring that programmer to learn a very cryptic and unreadable language.  It is interesting to note that until very recently assembler languages were still used to write operating system and database software.

Second generation systems were characterized by transistors.  This generation of systems gave rise to the first procedural languages that relied on high-level instructions that did not directly manipulate the computers' registers.  This was the start of a trend toward "high-level" languages that would take care of all of the low level machine operations, freeing the programmers to concentrate on the overall programming.

The third generation of computing hardware was characterized by the integrated circuit (IC), and heralded the introduction of computer languages that could be called user friendly.

Fourth generation hardware was characterized by Very Large Scale Integration (VLSI) of processors, and the languages became even friendlier and easier to program.  Fourth generation languages such as Oracle PL/SQL took care of all of the low-level programming, and left it to the programmer to concentrate on high-level program implementations.  This is the environment where Oracle began implementation of distributed database computing. 

Disk and Oracle Replication

Prior to the advent of cheap disk in the 1980, it was an important design consideration for all databases to minimize the amount of redundant information.  All databases were kept in centralized mainframe environments and distributed processing was very rare.

However, once disks became cheap enough to permit replicated data, Oracle introduced the concepts of "snapshots" and their first distributed database tool, called SQL*Net.  A snapshot is an Oracle construct whereby remote tables are refreshed from a master table.  This allows a table to be replicated on many Oracle databases.

SQL*Net allows geographically distributed databases to be "linked" such that they functioned as a single database.  The first version of SQL*Net was quite primitive when compared to Net8, but it did have the advantage of being simple and functional.