Planning the Database
As a DBA, you must plan:
1. The logical storage structure of the database and its physical implementation:
* How many disk drives do you have for this?
* How many data files will you need? (Plan for growth.)
* How many tablespaces will you use?
* Which type of information will be stored?
* Are there any special storage requirements due to type or size?
2. The overall database design
3. A backup strategy for the database
RoadToMaster – Each running Oracle database is associated with an Oracle instance. When a database is started on a database server, the Oracle software allocates a shared memory area called the System Global Area (SGA) and starts several Oracle background processes. This combination of the SGA and the Oracle processes is called an Oracle instance.
After starting an instance, the Oracle software associates the instance with a specific database. This is called mounting the database. The database is then ready to be opened, which makes it accessible to authorized users. Multiple instances can execute concurrently on the same computer, each accessing its own physical database.
You can look at the Oracle database architecture as various interrelated structural components.
An Oracle database uses memory structures and processes to manage and access the database. All memory structures exist in the main memory of the computers that constitute the database server. Processes are jobs that work in the memory of these computers. A process is defined as a “thread of control” or a mechanism in an operating system that can run a series of steps.
Database Structures consist of Memory Structure, Process Structure, and Storage Structure
RoadToMaster – Basically, there are two main components of Oracle database –– instance and database itself. An instance consists of some memory structures and the background processes, whereas a database refers to the disk resources. Figure 1 will show you the relationship.
Instance
As we cover above, the memory structures and background processes contitute an instance. The memory structure itself consists of System Global Area (SGA), Program Global Area (PGA), and an optional area –– Software Area Code. In the other hand, the mandatory background processes are Database Writer (DBWn), Log Writer (LGWR), Checkpoint (CKPT), System Monitor (SMON), and Process Monitor (PMON). And another optional background processes are Archiver (ARCn), Recoverer (RECO), etc. Figure 2 will illustrate the relationship for those components on an instance. Continue reading
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