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36 Cards in this Set

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When redo logs are used all previously committed transactions will be recovered; this is also known as being? All transactions that had modified data but had not been committed will be backed out; this is known as?
rolled forward, rolled back
It is recommended that you use which raid level on all redo log files?
raid 1
A checkpoint causes all in-cache data blocks that have not been written out to disk, to be written out to disk. These unwritten, changed buffers are called?
dirty buffers
When this operation is performed, the redo information is written into the redo log buffers.
commit
The redo log is made up of two or more redo log files that oracle automatically mirrors also referred to as?
log file group
If you are using disk mirroring to protect the redo log, it is not necessary to use this.
when a log file fills up and the log switch occurs, the file is copied to an
archive log file
A log switch always causes this to occur?
checkpoint
flushes all dirty buffers from the Oracle buffer cache
Each time a redo log file is reused, it is given a?
log sequence number
By having this, the RDBMS can keep track of which log file and archive log files have been used.
Select two. Which of the following parameters are used to control the checkpoint interval?
LOG_CHECKPOINT_INTERVAL, LOG_CHECKPOINT_TIMEOUT
how many blocks are there per 1mb?
2048
you want to force a checkpoint, you can do it with the following command:
alter system checkpoint;
As with the checkpoint, a log switch can be forced by hand. To do so, use the following command:
alter system switch logfile;
Complete the following command to delete the rollback segment log1.
ALTER DATABASE orcl drop logfile 'log1';
The redo log files are one of the few files in the Oracle database that are always written to in
sequential manner
It is better to have the archival process and redo log operation on?
separate disk volumes
sequential I/O is much faster than random I/O.
Using this for the redo log files because it offers the most protection and the fastest write performance.
raid 1
What is the advantage to isolating redo log files onto separate disk volumes?
faster i/o
These files are used in the startup of an instance to identify where the datafiles and redo log files are in the system.
control files
Which of the following commands will generate a new control file?
create controlfile
Each time you make changes to the structure of the database by adding datafiles, redo log files, and so on, run the command
ALTER DATABASE database BACKUP CONTROLFILE TO TRACE;
Records transactional information that will be used in the event that the transaction is rolled back.
rollback segments
keep the undo information that is used in rollback operations. Provide read consistency and used for database recovery.
Which of the following allows a long-running transaction to always obtain the same data within the query?
read consistency
The information written by the transaction to the rollback segments is held in?
rollback entries
stores information about which transactions use each rollback segment, and the rollback entries for each change performed by those transactions.
transaction table
You can manually assign a rollback segment by using the
set transaction command with the use rollback segment parameter
Where does the system keep the information written by the transaction to the rollback segments?
In rollback entries
There is a lot of rollback contention even though you are using your space efficiently. What is the problem?
Too many transactions sharing a rollback segment
A rollback segment must have at least how many extents
2
When a transaction uses the last extent in the segment, it looks to see whether the first extent is available. If the first extent is not available, what happens?
another extent is created
With rollback segments, the size for INITIAL should equal this so that all extents are the same size.
next
Select two. Which of the following CREATE ROLLBACK SEGMENT parameters control the size of the extents?
initial and next
A good rule of thumb is to create about "x" # of rollback segment for every "y" # of concurrent transactions.
x=1, y=4
Remember — the fewer transactions per rollback segment, the less contention
Rollback contention occurs when too many transactions try to use the same rollback segment at the same time, and some of them have to wait. You can tell whether you are seeing contention on rollback segments by looking at the dynamic performance table:
v$waitstat
Typically this rollback segment is not used, and you do not need to be concerned about it in re: to rollback contention.
system
In the v$sysstat, the number of requests for data is equal to
sum of DB BUFFER GETS and CONSISTENT GETS
If the number of waits for any of the rollback segment blocks or headers exceeds more than x% of the total number of requests, you should reduce the contention by adding more rollback segments.
1%