About redo log?

when i do some big transaction in a instance,ORACLE warnning me that:
oracle instance test - can't allocate log,archival required,
and if i close it,then when i connect to database test,ORACLE tell me ORACLE not available?
my question is why this happen and how can i deal with it?
thanks first!

Actually, if it says "archival required" it probably means that you are not 'automatically' archiving. You have probably set your database in archive mode by setting the ini.ora parameters, but that only tells oracle it cannot overwrite a log file before it is archived. At that point (when the online redologs are full) you can also not make new connections, except as sysdba.
I suggest you
connect / as sysdba
and
alter system archive log start
(this tells the instance to automatically archive from now on)
The log_archive_start = true in ini.ora will only automatically archive once turned on by "alter system archive log start" (to make sure you don't have to do an alter each time your bring down the instance). It will not turn it on for you if it hasn't been turned on by "alter system archive log start"
It could also be that your out of diskspace in your archive directory.
Hope this helps,
Lennert

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    1) My first question is..."Is there a way to run the
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    >
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    Message was edited by:
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    Absolutely not, they are not even remotely similar concepts.
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    EMC. http://www.emc.com No further commens on it.
    ~ Madrid
    http://hrivera99.blogspot.com

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    Edited by: user589812 on Dec 23, 2008 4:35 PM

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