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Oracle 12c function introduction
1. Data optimization includes automatic compression and tiering
2. Application sustainability enhancement
Transaction guard ensures understanding of transaction results
3. Statistical information enhancement
Level 11 dynamic sampling has been added, and level 11 dynamic sampling and mixed histograms are automatically turned on for parallel queries.
4. Easier top-n and paginated queries
Easier-to-use top-n and page number queries. Provides syntax similar to limit in mysql, row limiting clause
5. Enhanced row pattern matching
Provides a new pattern matching clause match_recognize, through which you can define regular grammar
6. Enhanced partition characteristics
Including drop and truncate partition operations for asynchronous maintenance of global index, as well as interval + reference partitioning method
7. Adaptive execution plan
This feature can be said to be magical. The final execution plan will be based on the rows obtained during execution, and the problems caused by column skew will be overcome.
8. New default values
Default can now directly refer to sequence, while enhancing the ability of default to serve as identity.
9. Increased size limit for varchar2 type, and primitive data type
varchar2, nvarchar2 and The upper limit of the size of raw data types can be extended to 32k, which is the same as its variable type in pl/sql. Of course, if it is too long, it may cause out of line storage like lob.
10.Better pl/sql sql
Embed pl/sql objects directly in sql and run it, guessing that sql engine and pl/sql engine may be optimized Interaction between 2 code engines to achieve less context switching than traditional sql call functions
11. Temporary undo cancellation
The undo data of the temporary table can be placed in temp, which helps to reduce the undo data in the undo table space and further reduces the generation of redo, thereby making active data The temporary table in guard allows dml. The setting method is: alter system/session set temp_undo_enabled=true|false
Oracle 12c software features
Operational structure
Control file: a binary file that stores information such as instances, data files, and log files. alter system set control_files=‘path’. V$CONTROLFILE.
Data file: stores data, with .dbf as suffix. In a word: one table space corresponds to multiple data files, and one data file corresponds to only one table space. dba_data_files/v$datafile.
Log files: Redo Log Files and Archivelog Files. Record database modification information. ALTER SYSTEM SWITCH LOGFILE; . V$LOG.
Parameter file: records basic parameters. spfile and pfile.
Warning file: show parameter background_dump_dest---use a shared server connection.
Trace file: show parameter user_dump_dest---use a dedicated server connection.
Oracle 12c Software Advantages
1. Built-in multi-tenancy
Each pluggable database is independent of other pluggable databases;resource Manager features have been extended to pluggable database
2. Several pluggable databases can be stored in a container database
To external applications and developers, pluggable databases appear to be ordinary databases prior to version 12.1; users access pluggable databases is the same as before when seeing a single database query
3. New management mechanism
The data administrator dba can connect to pluggable The database does not just manage the database; a special DBA can connect to the container database and manage it just like managing a single image file; each case in rac opens the container database and can choose what pluggable to open database
4.Benefits provided by pluggable databases features
Speed up the speed of reconfiguring the current database to a new platform; speed up the speed of fixing bugs and updating the current database; separate some responsibilities from the original DBA job responsibilities to application managers; centrally manage multiple databases; improve the scalability and fault protection of RAC; and Oracle SQL Developer and Oracle Enterprise Manager are relatively highly integrated
Oracle 12c change log
1: Optimized performance
2: We are serious about solving bug problems
Special instructions:
Baidu SkydiskExtraction code: dbi6
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