Overview of Oracle Architecture
From the Oracle Server Architecture Overview, I found an introduction to the Oracle architecture, which is used to describe the overall Oracle architecture.
Overview of Oracle Server Architecture
1 Oracle databases mainly consist of data file databases and database instance instances. The User links to the server process through the user process. When the database is started, it depends on the parameter file. If our database is in archive mode, the Oracle database will write redo log files to archived log files, avoid overwriting redo log files
2 instance Introduction
When the database starts, it reads the parameter file spfile and allocates a System globle area (SGA) according to the parameter file. Each Oracle Data session connection shares the memory, SGA can also be divided into shared pool, which stores some data dictionary caches and common function libraries. In SGA, database buffer cache, redo log buffer, java pool, and large pool are important.
Allocation of PGA and SGA: A session is generated every time a tcp connection is established to Oracle and a PGA is allocated. For SGA: memory shared by all session sessions. When the Oracle database is started, it will initialize and allocate a shared memory area. The size of the SGA will not change after it is started.
2 database files: data files, control files, Redo Log files. For data files, data files are mainly used to store business data, control files are used to store control files, and Redo log files are used to store database operation records, if the database is shut down due to an exception, the system reads Redo log files to fix the database at startup.
3. The database and instance of the Oracle database communicate with each other through a series of backend systems. Different operations are processed by different background processes.
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