QUESTION 58
While Monitoring the space usage in your database that is in ARCHIVELOG mode you observed that the flash
recovery area does not have enough free space to accommodate any more files and you do not have
necessary permissions to add more space to it.
Identify the two events that can occur in the eventof a log switch? (Choose two.)
A. An entry is created in the alert log file and the database instance continues to function normally
B. The log switch hangs occur for transactions until free space is available in the flash recovery area
C. The Oracle database server deletes a file that ison the obsolete file list to make free space in the flash
recovery area
D. The database instance status is implicitly changed to RESTRICTED mode and file creations to the flash
recovery area are prevented
Answer: BC
同636题：http://blog.csdn.net/rlhua/article/details/17258625
Explanation/Reference:
Section: Flashback Operations & Configuration
https://netfiles.uiuc.edu/jstrode/www/oraelmt/redo_log_files.html
Log Switch:
A log switch occurs when the database stops writing to one online redo log file and begins writing to another.
Normally, a switch occurs when the current online redo log file is full and writing must continue. However, you
can configure log switches to occur at regular intervals, regardless of whether the current online redo log file is
filled, and force log switches manually.
Incremental checkpoints:
An incremental checkpoint is a type of thread checkpoint partly intended to avoid writing large numbersof
blocks at online redo log switches. DBWn checks at least every three seconds to determine whether it has work
to do. When DBWn writes dirty buffers, it advances the checkpoint position, causing CKPT to write the
checkpoint position to the control file, but not tothe data file headers.