Redo logs
Oracle database contains redo log groups which in turn hold redo log members.
There could be multiple members which belong to a group. When oracle writes
data to the group it can parallelize writing operation to the
members, failure to write in one of the members of the group does
not cause failure in the database as long as one of the member is available
for writing.
An archived redo log file is a copy of one of the filled members of a redo log
group. The archived log contains a copy of every group created since archiving
was enabled.
In 10g the LOG_ARCHIVE_FORMAT : %t_%s_%r stands for
%t=thread, %s=log sequence, %r=database incarnation
Example:-
/u02/app/oracle/oradata/payroll/1_1_580756371.dbf
/u02/app/oracle/oradata/payroll/1_3_580756371.dbf
/u02/app/oracle/oradata/payroll/1_6_580760234.dbf
/u02/app/oracle/oradata/payroll/1_7_580760234.dbf
In the above archived log’s first two files are from one incarnation of the
database while the other two are from another incarnation of the database.
The value of LOG_ARCHIVE_MIN_SUCCEED_DEST
determines the minimum number of places where the files should be archived.
1.1. How do you move the location of redolog?
It is a five step process
• Shutdown the database
• copy the redo log files to new location
• startup the database but do not mount it.
• rename the log members
open the database for normal operation
