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RE: oracle clustering

From: Murali Vallath <murali_vallath_at_hotmail.com>
Date: Wed, 29 Nov 2000 21:35:04 -0500
Message-Id: <10695.123281@fatcity.com> 





Cache fusion is supposed to eliminate pinging completely. This was promised 
in 8i now it is a new feature in 9i.



I don't think this should be a difficult feature. I really don't understand 
why Oracle is having such a tough time figuring this out. It's been in place 
for many years in VMS /DEC Clustering and with Oracle Rdb. Infact Compaq is 
now offering this feature with their Tru64 boxes.



Hay, we may not need OPS anymore?



We are testing this feature currently, cluster failover without OPS.



Murali Vallath


Oracle Certified DBA


http://www8.ewebcity.com/muralivallath/


http://www.summerskyus.com/



From: Alex Hillman <alex_hillman_at_physia.com>
Reply-To: ORACLE-L_at_fatcity.com


To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
Subject: RE: oracle clustering


Date: Wed, 29 Nov 2000 13:50:52 -0800



I do not understand how it will go away entirely. Alleviated maybe. My
understanding that pinging will continue to occur but not thru disk but
moving buffers thru fast interconnect.



Alex Hillman



-----Original Message-----



Sent: Wednesday, November 29, 2000 2:41 PM
To: Multiple recipients of list ORACLE-L




What Chuck says is true to a point.  However, they failover
and recovery times for and OPS cluster and
a non-ops cluster can be significantly different.



We use HP ServiceGuard clustering and OPS.



A failover using OPS takes


about 30 seconds at most (for us) and requires
NO manual intervention to accomplish the reocovery.



A failover using ServiceGuard Clustering
takes about 10-15 minutes and may


(under rare circumstances) require


manual intervention to accomplish the recovery.



Also, pinging became less of a problem with the
dynamic PCM locking (8.0) and even less of an
issue with Cache Fusion (8.1.6).  Supposedly,
it goes away entire with 9i.







R. Matt Adams  - GE Appliances - matt.adams_at_appl.ge.com


   It will make sense when you stop thinking logically
   and start thinking Oracle-ly    -  Jim Droppa





-----Original Message-----



<mailto:chuck_hamilton_at_yahoo.com> ]


Sent: Wednesday, November 29, 2000 12:21 PM
To: Multiple recipients of list ORACLE-L





Then the answer is no. Oracle clustering is not the same as OPS. OPS is not
necessary for high availability either, though it does make the database
more highly available then single instance oracle on a cluster.



I once thought OPS gave you 100% availability because multiple instances
were running on separate machines sharing the same physical database. If one
machine or instance failed, the others continued to run uninterruppted. The
2nd (and 3rd, 4th,... Nth) instances do continue to run but there is an
interruption in service when any one instance fails. There is a period of
time known as a "brown out" where *no* work can be done on the database.
During that time the DLM (distibuted lock manager) which controls
concurrency between the instances must reconfigure itself to run accross
only the surviving instances. Then an instance recovery must be performed on
behalf of the failed instance. Only after this is done can work continue on
the database. When the failed instance comes back online the DLM must be
reconfigured again to include the new instance. OPS is also only available
on a few platforms (IBM, HP, SUN, and Compaq).



Single instance oracle clustering OTOH is implemented entirely through the
platforms cluster management software. The instance runs on only one node at
a time. Should the instance or node fail, the cluster manager software shuts
the instance down, unmounts the disks, remounts them on another node, and
starts the oracle instance on that node.



Single instance oracle running on a cluster manager is still highly
available and much easier to administer than OPS. For example, your
application must be redesigned around OPS. In order to reduce pinging of
blocks between nodes (which requires physical disk i/o much of the time),
you need to segregate your apps and users amongst the nodes in such a way as
to eliminate reduce the chance that multiple nodes will need access to the
same database blocks. This is not always an easy task. If you don't do this
you could see your performance go down the toilet even though you're adding
more nodes and cpus. Trying to identify contention between instances is not
an easy task either.



Having been to the OPS class and actually working with it, I'm not convinced
it buys me enough availability to warrant it's use instead of single
instance oracle on a cluster. Either way when an instance fails you have to
perform instance recovery. The only thing OPS saves you is the time it takes
to move the disk mounts and start an instance. And the cost for that small
amount of time is an application redesign. Only data warehouses typically
can be dropped righ on to OPS with little or no changes because of there
read-only nature.



HTH


Chuck Hamilton




   Herman <Sherman_at_bcsis.com> wrote:








what i mean is the clustering to obtain high availability.



and i heard this can be achieved thru OPS,



anyone can comment about this ?





thanks &



regards





Herman










To: Multiple recipients of list ORACLE-L <mailto:ORACLE-L_at_fatcity.com>



Sent: Tuesday, November 28, 2000 1:25 AM







I'm not sure what you're referring to by "oracle clustering". Is this a
product you've heard of? I'm not familiar with it. Inside the database,
clustering is the term for nesting multiple tables within the same segment
for faster joins. Could that be what you're thinking about? Outside the
database, clustering is a means of attaining high availability and is
required for OPS. Single instance Oracle can also run on a cluster apart
from OPS but is not quite as highly available.




Herman <Sherman_at_bcsis.com> wrote:





hello all,



can somebody plz help me to explain about oracle clustering ?
is oracle clustering equal to Oracle Parallel Server ?
is it considered as software clustering ?



wha'ts the different, advantage and disadvantage bettween software
clustering and hardware clustering anyway ?
can we combine those two when we implement OPS ?




thanks


and regards


Herman



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Author: Herman


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Author: Adams, Matthew (GEA, 088130)


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