Learn the following in this article:
It is possible to describe the system structure of the Oracle8i server and its main components.
Oracle8i's system structure is shown in the figure below, I believe that everyone is very familiar with this picture :)
Oracle8i is an object-oriented relationship database management system, which is an introduction to its main components:
1. Oracle Instance (Oracle Instance)
Oracle instance consists of a set of background processes and memory regions. In order to access data, the instance must be started. Every instance is started, accompanied by the allocation of System Global Are (SGA) and the start of the background process.
SGA consists of the following components
Share pool (including a Dictionary buffer SQL statement buffer)
Data Buffer Cache (first written to the buffer) when changing the database content)
Redo log buffer (saved to the buffer before the recording of the physical file)
Backstage process that must be started in Oracle8i
DBWR (Data Write Process) writes the data in the changed buffer to the data file.
LGWR (log write process) writes the data in the recovery log buffer to the reconciliation log file.
SMON (System Monitoring Process), for example, when the database is started, the call is automatically recovered.
PMON (Process Monitoring Process) If an Oracle process fails, the PMON process clears the process
Occupied resources.
CKPT (Checkpoint Process) Change the database control file. (My understanding)
2. Database file
Database files are operating system files that store database data.
3. Other files
Including parameter files, reconciliation log files, archive log files, control files, password files, etc. Only the database has an archive log file in archiving mode.
