ORACLE SUMMARY

Storage is composed of 1 or more table spaces composed of 1 or more database files. Every Oracle database has a table space named SYSTEM. Each database file is composed of segments (or objects): table objects, index segments, rollback segments, temporary segments and cache segments. Segments are composed of Oracle blocks, which can be in defferent database files. Contiguous blocks in a database file composing an object are called an extent. The first extent is 5 blocks, and grows as needed. Blocks are only released when an object is dropped. Blocks can vary from 1K(DOS) to 4K(mainframe). UNIX uses 2K blocks. Blocks are managed by the data dictionary.

The background process, SMON, does auto-coalescing of fragmented free blocks.

A 3-tier application in Oracle uses NCA (network Computing Architecture). Tier 1 is the client, tier 2 is the Universal Application Server, and tier 3 is the Universal Data Server.