Answer Posted / kittu_chintu2005
In LMT: A tablespace that manages its own extents maintains a bitmap in each datafile to keep track of the free or used status of blocks in that datafile. Each bit in the bitmap corresponds to a group of blocks. When an extent is allocated or freed for reuse, Oracle changes the bitmap values to show the new status of the blocks. These changes do not generate rollback information because they do not update tables (like sys.uet$, sys.fet$) in the data dictionary (except for special cases such as tablespace quota information).
When you create a locally managed tablespace, header bitmaps are created for each datafile. If more datafiles are added, new header bitmaps are created for each added file.
In DMT:In DMT, to keep track of the free or used status of blocks, oracle uses data dictionary tables. When an extent is allocated or freed for reuse, free space is recorded in the SYS.FET$ table, and used space in the SYS.UET$ table. Whenever space is required in one of these tablespaces, the ST (space transaction) enqueue latch must be obtained to do insert and deletes against these tables. As only one process can acquire the ST enque at a given time, this often lead to contention. These changes generate rollback information because they update tables (like sys.uet$, sys.fet$) in the data dictionary.
| Is This Answer Correct ? | 11 Yes | 2 No |
Post New Answer View All Answers
What are the different ways you can create databases in sql server? : sql server DBA
What would you do with an "in-doubt" distributed transaction?
how can you communicate with operating system files from oracle?
What is a correlated sub-query? : sql server DBA
Database crashes. Corruption is found scattered among the file system neither of your doing nor of Oracle's. What database recovery options are available? Database is in archive log mode.
What are the different types of upgrades that can be performed in sql server? : sql server DBA
What is transparent data encryption? : sql server DBA
What are the new features in sql server 2005 when compared to sql server 2000? : sql server DBA
Claims and Drains are the locks used to control the concurrency between SQL processes and utilities. Referring to the above statement, what is the maximum number of concurrent Claimers for a Subsystem? Choice 1 32 Choice 2 64 Choice 3 128 Choice 4 256 Choice 5 No limit
Why would you call update statistics? : sql server DBA
What is dcl? : sql server DBA
What is the default fill factor value? : sql server DBA
how can you implement fine-grained auditing?
what do you understand by flashback feature of oracle?
what is logical system in sap basis
