Jay,
A1-
the log_archive_start parameter simply will determine if you are in
automatic or manual archive mode. This parameter does not put the
database into archivelog mode, it determines if the archive process (ARCn)
backups the redo log files when a log switch is performed. If you set
this parm to TRUE, then the ARCn process will automatically backup your
redo log files. If you take the default value of false, then you must
manually force the redo logs to be archived by executing the command ALTER
SYSTEM ARCHIVE LOG <some parm> (ex: ALTER SYSTEM ARCHIVE LOG ALL;). Now
even if you set this parameter, if you do not execute the ALTER DATABASE
ARCHIVELOG command, then this paramater does not do anything.
A2-
The transactions are still written to the datafiles by DBWR. The
difference is that the header is not updated with checkpoint information.
So the datafiles that are in backup mode are inconsistent with the
controlfile. When you issue the alter tablespace tsname end backup; that
takes the freeze off the datafile header, so the next checkpoint will be
recorded in the datafile header bringing the datafile back in sync with
the rest of the database.
Hope this helps....
Chris
"j" <oracledba-ezmlmshield-x52946469.[Email address protected]
09/14/04 03:57 AM
To: "LazyDBA Discussion" <[Email address protected]
cc:
Subject: archivelog and hot back
Dear All,
I have two specific queries:
1) While changing from noarchivelog mode to archivelog mode , why it is
necessary to do "alter database open archivelog" even if log_archive_start
=true is set in the init.ora file.
2) During hot back when we give "alter tablespace <TSname> begin backup",
the header of datafiles are freezed, then where are transactions
associated with these datafiles are written?
Jay
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