failure of storage containing another copy of oracle redo and archive logs

[Jawed Akhtar]

Hi,
1. Could we keep multiple redo and archive logs on different storages attaced to hosts via SAN.
2. What would happen if any one location (storage) containing second archive nad redo logs is unavailaible. The main file system containing database and first copy of remain avialable. Would the database continue to work or will hang.
Thanks in advance.

Regd
Jawed Akhtar

[Eric Antunes · Accepted solution]

Hi Jawed,

1- Yes you can and you must. Duplexing is recomended for redologs and archivelogs because a disk failure won't crash your database. Create at least 2 redolog groups with 2 logfile members, each in a different storage. Use log_archive_dest and log_archive_duplex_dest to define both archivelog destinations. If you need more help defining redolog groups and members don't hesitate.

2- The database will continue if you have log_archive_min_succeed_dest=1.

Best Regards,

Eric Antunes

[Eric Antunes]

2- The database will continue if you have log_archive_min_succeed_dest=1 and, of course, the datafiles are not located in the bad storage...

[Jawed Akhtar]

Thanks Eric,
You have told that database will continue to work if any one of archive destiantion is avaialble by enabling parameter LOG_ARCHIVE_MIN_SUCCEED_DEST = 1 .

1. What about redo logs. Is there any parameter which ensures that databse will continue to work if any one of destinations for redo logs fails in case of redolog multiplexing.


Thanks

[Yogeeraj_1]

hi,

Please note that if Oracle cannot write to a redo log file at any one time, that log file can no longer be trusted, and Oracle marks it as "STALE". This indicates that the log file cannot be relied upon to provide all the data written to the log.

In general, the stale status of a redo log member should not be a cause for great concern, unless you observe that this happens too frequently.

Note that, a stale log is not necessarily an invalid log, but more of an "in-doubt" one. Once the corresponding redo group becomes the current one again, the stale status will go away by itself.

Mirroring your redo logs reduces the risks associated with a stale log file.

hope this helps too!

kind regards
yogeeraj

[Jawed Akhtar]

Thanks yoogeraj,

1. We have alocated some space from two separate storages devices on SAN to one server runing oracle. One strage has main file system for oracle database and its redo and archive files. Another secondary storage has a copy of redo logs and archive logs. Few days ago the secondary storage was unavaialble on SAN due to some fibre cable problem.
2. We observed that oracle hanged due to missing path of secondary storage having another copy of redo log files.

I would like to know

a. Was it due to unavailibilty of secondary redo logs or something else.
b. Is there any way or parameter to ensure that oracle will contiune to work even secondary stroage is abruplty removed or unavailable.

Thanks
Jawed Akhtar

[Eric Antunes]

Hi Jawed,

You must also have the control files duplexed...

Can you post the following query results (?):

select name, value from v$parameter where name like '%archive%'
union
select name, value from v$parameter where name like '%control_files%';

And

select * from v$logfile;

Best Regards,

Eric Antunes

[Jawed Akhtar]

Hi Eric,
Yes we have control files duplexed as well,
But I am unix administrator, So I don't access ORacle database.

My questions remains same. Could you give me a genral idea about my aforesaid questions. Does the duplexing of control files have any effect in availibilty of database if one location containing copies of redo and control files fails.

Thanks and Regards
Jawed Akhtar

[Eric Antunes]

"Does the duplexing of control files have any effect in availibilty of database if one location containing copies of redo and control files fails."

Yes it have: duplexing ensure your database will continue up!

What you get is invalid redolog files at that failed location (but database continues to write to the good ones):

GROUP# STATUS MEMBER
2 /disc1/oradata/TST/log2a.dbf
1 /disc1/oradata/TST/log1a.dbf
2 INVALID /disc2/app/oracle/TST/log2b.dbf
1 INVALID /disc2/app/oracle/TST/log1b.dbf
3 /disc1/oradata/TST/log3a.dbf
3 INVALID /disc2/app/oracle/TST/log3b.dbf

If you don't have duplexing and the location of redologs and/or control files fails, your database crashes...

Best Regards,

Eric Antunes

[Jawed Akhtar]

Thanks Eric,
Any good link to conecpts of Redo and control file multiplexing in Oracel 9i Database.

Regd
Jawed Akhtar