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Home -> Community -> Mailing Lists -> Oracle-L -> Re: oracle clustering
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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
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
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Herman INET: Sherman_at_bcsis.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include! ! a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). --------------------------------- Do You Yahoo!? Yahoo! Shopping - Thousands of Stores. Millions of Products. --------------------------------- Do You Yahoo!? Yahoo! Shopping - Thousands of Stores. Millions of Products. --0-1681692777-975518400=:6950 Content-Type: text/html; charset=us-asciiReceived on Wed Nov 29 2000 - 11:20:00 CST
<P> 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. </P>
<P>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).</P>
<P>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.</P>
<P>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. </P>
<P>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.</P>
<P>HTH</P>
<BLOCKQUOTE style="MARGIN-RIGHT: 0px">
<P>Chuck Hamilton<BR></P></BLOCKQUOTE>
<P> <B><I>Herman <Sherman_at_bcsis.com></I></B> wrote: <BR></P>
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<DIV><FONT face=Arial size=2>what i mean is the clustering to obtain high availability.</FONT></DIV><BR>
<DIV><FONT face=Arial size=2>and i heard this can be achieved thru OPS,</FONT></DIV><BR>
<DIV><FONT face=Arial size=2>anyone can comment about this ?</FONT></DIV><BR>
<DIV> </DIV><BR>
<DIV><FONT face=Arial size=2>thanks &</FONT></DIV><BR>
<DIV><FONT face=Arial size=2>regards</FONT></DIV><BR>
<DIV> </DIV><BR>
<DIV><FONT face=Arial size=2>Herman</FONT></DIV><BR>
<DIV> </DIV><BR>
<BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"><BR>
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV><BR>
<DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B> <A href="mailto:chuck_hamilton_at_yahoo.com" title=chuck_hamilton_at_yahoo.com>Chuck Hamilton</A> </DIV><BR>
<DIV style="FONT: 10pt arial"><B>To:</B> <A href="mailto:ORACLE-L_at_fatcity.com" title=ORACLE-L_at_fatcity.com>Multiple recipients of list ORACLE-L</A> </DIV><BR>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, November 28, 2000 1:25 AM</DIV><BR>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: oracle clustering</DIV><BR>
<DIV><BR></DIV><BR>
<P>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.</P><BR>
<P><B><I>Herman <Sherman_at_bcsis.com></I></B> wrote: <BR></P><BR>
<BLOCKQUOTE style="BORDER-LEFT: #1010ff 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px">hello all,<BR><BR>can somebody plz help me to explain about oracle clustering ?<BR>is oracle clustering equal to Oracle Parallel Server ?<BR>is it considered as software clustering ?<BR><BR>wha'ts the different, advantage and disadvantage bettween software<BR>clustering and hardware clustering anyway ?<BR>can we combine those two when we implement OPS ?<BR><BR><BR>thanks<BR>and regards<BR>Herman<BR><BR>-- <BR>Please see the official ORACLE-L FAQ: http://www.orafaq.com<BR>-- <BR>Author: Herman<BR>INET: Sherman@bcsis.com<BR><BR>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051<BR>San Diego, California -- Public Internet access / Mailing Lists<BR>--------------------------------------------------------------------<BR>To REMOVE yourself from this mailing list, send an E-Mail message<BR>to: ListGuru@fatcity.com (note EXACT spelling of 'ListGuru') and in<BR>the message BODY, include!
! ! a line containing: UNSUB ORACLE-L<BR>(or the name of mailing list you want to be removed from). You may<BR>also send the HELP command for other information (like subscribing).</BLOCKQUOTE><BR>
<P><BR><BR>
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