Oracle Expert Advanced Programming Learning notes (ii)

Oracle| Notes | programming | advanced
3 main components of Oracle architecture:
1. File: 5 files (parameter files, control files, data files, temporary data files, redo log files) that make up the database instance
2. System global Zone SGA (Systems Global Area): Java pool, shared pool, etc.
3. Physical processes and Threads: running 3 different types of processes on the database (server server process, background backgroud process, subordinate slave process)

Terminology Explanation:
Database: A collection of physical operating system files
Instance: a set of Oracle processes and SGA
The relationship between the two:
A database can be loaded by multiple instances mount and open
Instance can load and open a separate database in a timely manner, and the database opened and loaded by the instance does not have to be the same at startup

File:
1. parameter file:
TNSNAMES. ORA, LISTENER. Ora,sqlnet. ORA, PROTOCOL. Ora,names. ORA, Sman. ORA, LDAP. ORA
(Refer to "Oracle Net Administrator Guide")
$ORACLE _home/dbs/int<oracle_sid>.ora: Content is a series of variable names and value pairs
such as:
Db_name= "Wmdb"
db_block_size=8192
control_files= ("C:\oradata\control01.ctl", "C:\oradata\control02.ctl")
...
Some of the parameters that are not described in the Oracle document begin with an underscore
In addition to setting the _trace_files_public=true parameter in the development environment, other parameters that are not described are best not to be changed

2. Data files:
Database database--> table Space tablespace-->segment segment-->extent extension area-->block block
1 The database consists of one or more table spaces
2 table space consists of one or more data files, one table space with one or more segments
3 A Segment (table, index, etc.) consists of multiple extents, Gencun in a tablespace, but can have data in multiple data files in a tablespace.
4 An extension is a contiguous chunk of space on disk, an extension in a tablespace, and always a single file in the Tablespace
5 block is the smallest allocation unit and I/O unit in the database, and its size is fixed when the database is created.

3. Temporary documents
When memory is not sufficient to hold intermediate results (sets) of a large-scale sort operation, Oracle stores them with temporary files, and permanent data such as tables or indexes are not stored in temporary files, but the contents of temporary tables or temporary indexes may be stored in temporary files

It is recommended to configure a database using local administration temp table Space???, Example
Create Temporary Tablespace Temp
Tempfile ' c:\oracle\oradata\walter\temp.dbf '
Size 5m
Extent Management Local
Uniform size 64k

4. Control file
A fairly small file, up to 64M, containing a directory of other files required by Oracle
Data file Init<sid>.ora tells the instance to control the location of the file
The control file tells the example of the location of the database and the online redo log files
The control file also provides Oracle with additional information, such as checkpoint, database name, timestamp of database creation, archive redo log history, etc.

5. Redo Log Files
The transaction log for the data, which is only used when restoring
1) Online redo log
2 Archive Redo Log

Memory structure
1.SGA (System Global area)
2.PGA (Process Global area)
3.UGA (User Global area)
Cond