Resize Redo Log

Here is a newly created database redo log information:

SQL> select * from v$log;

———- ———- ———- ———- ———- — —————- ————- ——————-
1 1 17 52428800 1 NO INACTIVE 996238 06/09/2007 22:01:59
2 1 18 52428800 1 NO INACTIVE 1006432 06/09/2007 22:13:32
3 1 19 52428800 1 NO CURRENT 1036439 07/09/2007 09:56:44

SQL> select * from v$logfile;

———- ——- ——- ————————————————-
3 ONLINE /database/data/redo03.log
2 ONLINE /database/data/redo02.log
1 ONLINE /database/data/redo01.log

Here is how i changed this to five 200M redo logs:

SQL> alter database add logfile group 4 (‘/database/data/redo04.log’) size 200M;
SQL> alter database add logfile group 5 (‘/database/data/redo05.log’) size 200M;

while running following sql commands, if you hit an error like this:

ORA-01623: log 3 is current log for instance RPTDB (thread 1) – cannot drop
ORA-00312: online log 3 thread 1: ‘/database/data/redo03.log’

you should run ” alter system switch logfile;” until current log is 4 or 5. Then execute “alter system checkpoint;”

SQL> alter database drop logfile group 1;
SQL> alter database drop logfile group 2;
SQL> alter database drop logfile group 3;

then move (or maybe drop) old redo logs

mv /database/data/redo01.log /database/data/redo01_old.log
mv /database/data/redo02.log /database/data/redo02_old.log
mv /database/data/redo03.log /database/data/redo03_old.log


SQL> alter database add logfile group 1 (‘/database/data/redo01.log’) size 200M;
SQL> alter database add logfile group 2 (‘/database/data/redo02.log’) size 200M;
SQL> alter database add logfile group 3 (‘/database/data/redo03.log’) size 200M;

How to check default temporary tablespace

COLUMN property_name FORMAT A30
COLUMN property_value FORMAT A30
COLUMN description FORMAT A50

FROM database_properties
WHERE property_name like ‘%TABLESPACE’;

short topic but hope it will be useful
Thank you
Osama Mustafa

Backup an entire hard disk using dd command

The ‘ dd ‘ command is one of the original Unix utilities and should be in everyone’s tool box. It can strip headers, extract parts of binary files and write into the middle of floppy disks; it is used by the Linux kernel Makefiles to make boot images. It can be used to copy and convert magnetic tape formats, convert between ASCII and EBCDIC, swap bytes, and force to upper and lowercase. 

# dd –help

full hard disk copy

dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz

Hdx could be hda, hdb etc. In the second example gzip is used to compress the image if it is really just a backup.  

Restore Backup of hard disk copy

dd if=/path/to/image of=/dev/hdx

gzip -dc /path/to/image.gz | dd of=/dev/hdx  

MBR backup

In order to backup only the first few bytes containing the MBR and the partition table you can use dd as well.

dd if=/dev/hdx of=/path/to/image count=1 bs=512 

MBR restore

dd if=/path/to/image of=/dev/hdx

Add “count=1 bs=446” to exclude the partition table from being written to disk. You can manually restore the table.

 “All This Information was taken from the other site , just for information to take hard-disk backup , it will be useful to use it with Oracle ”

thank you 
Osama mustafa