Backup: Can be performed while the database is open. Briefly describe what is SYSTEM & NON-SYSTEM tablespace?
SYSTEM Tablespaces Created with the database Required in all databases Contains the data dictionary, including stored program units Contains the SYSTEM undo segment Should not contain user data, although it is allowed Non-SYSTEM Tablespaces Enable more flexibility in database administration Separate undo, temporary, application data, and application index segments Separate data by backup requirements Separate dynamic and static data Control the amount of space allocated to user’s objects ANSWER 7: Locally managed tablespaces: o Free extents recorded in bitmap o Each bit corresponds to a block or group of blocks o Bit value indicates free or used Dictionary-managed tablespaces: o Default method o Free extents recorded in data dictionary tables LOCALLY MANAGED TABLESAPCES: Locally managed tablespaces track all extent information in the tablespace itself by using bitmaps CREATE TABLESPACE userdata DATAFILE ‘/u01/oradata/userdata01.dbf’ SIZE 500M EXTENT MANAGEMENT LOCAL UNIFORM SIZE 256K; Reduced contention on data dictionary tables No undo generated when space allocation or de-allocation occurs No coalescing required DICTIONARY MANAGED TABLESPACES: CREATE TABLESPACE userdata
DATAFILE ‘/u01/oradata/userdata01.dbf’ SIZE 500M EXTENT MANAGEMENT DICTIONARY DEFAULT STORAGE ( initial 1M NEXT 1M ); Extents are managed in the data dictionary Each segment stored in the tablespace can have a different storage clause Coalescing required ANSWER 8: Every Oracle Database must have a method of maintaining information that is used to roll back, or undo, changes to the database. Such information consists of records of the actions of transactions, primarily before they are committed. These records are collectively referred to as undo .
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- Spring '18
- Oracle Database, Redo log