The Online Redo Logs
As sessions interact with the Oracle Database 10g, the details of their activities are recorded in the online redo logs. Many people think of these as the transaction logs. A transaction is a unit of work, passed to the database for processing. Oracle 10g insists that there are at least two online redo logs to support the instance. In fact, most databases have two or more redo log groups with each group having the same number of equally sized members.
The SYSTEM Tablespace
Tablespace is a fancy Oracle Database 10g name for a database file.
As Oracle Database 10g operates, it continually gets operational information out of its data dictionary and, as records are created, this system tablespace defines attributes of the data it stores, such as:
- The data type of pieces of information. Are they numeric, alphanumeric, or perhaps binary of some video or audio format?
- The maximum allowable size of fields as they are populated by the applications. This is where, for example, a country description is defined as from one to 30 characters long, and containing only letters.
- Who owns the information as the database data files are populated?
- Who is allowed to look at each other's data and what types of activities each user of the database can perform on that data?