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When a Tablespace is in Backup mode the SCN of its Datafiles (which is located on the header of the datafile) is frozen. More over, the redo generation is modified so as to be able to recover from fractured blocks.
Else, the blocks of the datafile can be modified / written as usual.
tablespace backup mode is old method due to excessive redologs
pls use rman And then backup tablespace online.
The biggest advantage of RMAN is that it only backup used space in the database. RMAN doesn't put tablespaces in backup mode, saving on redo generation overhead. RMAN will re-read database blocks until it gets a consistent image of it.
yes. additionally as Lubies said, redo log generation changes, in this case redo log generation increases, as instead of change deltas, entire changed block is written to the redo log files.That is why it is strongly recommended to put the tablespaces out of hot backup mode upon finishing the backup- copying usually.
does Oracle write to data files in begin/hot backup mode?
When a tablespace is in backup mode, Oracle will stop updating its file headers, but will continue to write to the data files.
When in backup mode, Oracle will write complete changed blocks to the redo log files. Normally only deltas (change vectors) are logged to the redo logs. This is done to enable reconstruction of a block if only half of it was backed up (split blocks). Because of this, one should notice increased log activity and archiving during on-line backups.
To solve this problem, simply switch to RMAN backups.
hope this helps