RE: Re[2]:Your views on Quest - Shareplex
Bear in mind, Oralce is not always 100% accurate, specially when something competes with their product. Walking on water and developing software from a specification are easy if both are frozen. Christopher R. Spence Oracle DBA Fuelspot -Original Message- Sent: Tuesday, May 29, 2001 5:06 PM To: Multiple recipients of list ORACLE-L Jim, Thanks, just assures me that it is NOT a product that I want around. Dick Goulet Reply Separator Author: Jim Hawkins [EMAIL PROTECTED] Date: 5/29/2001 11:01 AM All, We are currently as customer of Quest Software using LiveReorg and Spotlight. For those who don't know, LiveReorg is a combination of two existing Quest products, Space Manager and SharePlex. I asked the exact same question regarding the mining of redo logs of our Quest sales rep. I thought all would be interested in the reply. It is a in-line reply to an Oracle MetaLink document. Jim Hawkins Lead SAPR/3 Oracle Database Administrator MEMC Electronic Materials, Inc. 600 Pearl Drive St. Louis, MO 633376 9636) 474-7832 [EMAIL PROTECTED] (work) [EMAIL PROTECTED] (home) Doc ID: Note:97080.1 Subject: Extracting Data from Redo Logs Is Not A Supported Interface Type: BULLETIN Status: PUBLISHED Content Type: TEXT/PLAIN Creation Date: 22-JAN-2000 Last Revision Date: 17-FEB-2000 Language: USAENG PURPOSE --- To explain why any extraction of data from redo logs is not supported. SCOPE APPLICATION --- Customers who are considering using Quest SharePlex for disaster recovery. Extracting Data from Redo Logs Is Not A Supported Interface -- Quest SharePlex for Oracle replicates data to one or more other Oracle instances. It attempts to use the information in the redo log to replicate transactions remotely. 1) There is not sufficient information in the logs to logically replicate transactions, so the data applied to the destination system may be different from the primary, and therefore inaccurate. Eyal: That is correct. A part of the SharePlex product goes back to the source database and completes the missing information. This is done only for certain types of Update statements but is not nessasery for Inserts and Deletes. 2) Reading the redo log is not a supported interface. From the very beginning, Oracle has changed redo log formats to support functional enhancements. We must therefore reserve the right to continue to make needed log format changes. For this reason, certification of any third party product using this interface is not possible. Since this is an unsupported interface, the accuracy or completeness of the data in the destination database can not be assured. Eyal: The power of the product is the direct result from reading the raw log data. It is our core competency in Quest to understand and support the changing nature of the Oracle log. The reality is that between version 7.0 until 8.1.6 there where only minor changes to the log. Since we are a close partner with Oracle we get early releases of the software and we have the chance to update the product as needed. So far this has never been an issue since most large production sites are running Oracle versions that are atleast 6 months to a year old. Regarding assurance to the completeness of the data, we do not expect Oracle to provide any assurance. Quest is the one that assures the content of the destination. Quest support has some of the best support experts in the business. Any problem with the database content should be directed to our support organization and not Oracle World Wide Support. Likelihood of Occurrence ~ Unknown. However, even a low likelihood is a concern for disaster recovery (DR). In disaster failovers, the remote server's database may be the only viable copy. Eyal: Since Oracle uses the data in the log to perform database recovery, all the information necessary to create a point in time image of the database exists in the log. However, we believe that SharePlex has a better chance to survive a disaster than even a database recovery. This is because SharePlex only needs the data to recover a transaction while Oracle needs all changes present in the log, including index and rollback changes, to successfully recover a database. An index block corruption may render the recovered database useless. History indicates that SharePlex can withstand most log corruptions and data block corruptions, while maintaining a viable live standby site. If the client is not a 100% sure, SharePlex provides a variety of mechanisms to periodically resync the standby database, including the ability to use a hot backup and 3rd party disk mirroring
Re: Re[2]:Your views on Quest - Shareplex
I would guess that Oracle is just covering their collective arses, by putting that stuff out. So some junior wannabe coder (like me) doesn't start writing his own log-based replication software - then suing Oracle when they change something. I believe that Oracle actually works with Quest as a partner (thought I read that somewhere, maybe www.quest.com). Anyway, we use Shareplex quite a bit. For simple, one-way, DR replicaction (no users in the target) it's very robust. For a reporting scenario (off-loading reporting processes to a seperate schema, one-way replication) it's still pretty good as long as you can *keep users from changing the data on the target instance*. As you get into more complicated implementations (bi-directional, etc.) you need to think things out more carefully, and have more DBA resources available for monitoring, conflict resolution procedures, etc. Quest's support is very good, in my opinion. They've written patches for us a few times with very short turnaround... Just my 2 cents... Have a good one! - Jerry - Original Message - To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED] Sent: Tuesday, May 29, 2001 5:06 PM Jim, Thanks, just assures me that it is NOT a product that I want around. Dick Goulet Reply Separator Author: Jim Hawkins [EMAIL PROTECTED] Date: 5/29/2001 11:01 AM All, We are currently as customer of Quest Software using LiveReorg and Spotlight. For those who don't know, LiveReorg is a combination of two existing Quest products, Space Manager and SharePlex. I asked the exact same question regarding the mining of redo logs of our Quest sales rep. I thought all would be interested in the reply. It is a in-line reply to an Oracle MetaLink document. Jim Hawkins Lead SAPR/3 Oracle Database Administrator MEMC Electronic Materials, Inc. 600 Pearl Drive St. Louis, MO 633376 9636) 474-7832 [EMAIL PROTECTED] (work) [EMAIL PROTECTED] (home) Doc ID: Note:97080.1 Subject: Extracting Data from Redo Logs Is Not A Supported Interface Type: BULLETIN Status: PUBLISHED Content Type: TEXT/PLAIN Creation Date: 22-JAN-2000 Last Revision Date: 17-FEB-2000 Language: USAENG PURPOSE --- To explain why any extraction of data from redo logs is not supported. SCOPE APPLICATION --- Customers who are considering using Quest SharePlex for disaster recovery. Extracting Data from Redo Logs Is Not A Supported Interface -- Quest SharePlex for Oracle replicates data to one or more other Oracle instances. It attempts to use the information in the redo log to replicate transactions remotely. 1) There is not sufficient information in the logs to logically replicate transactions, so the data applied to the destination system may be different from the primary, and therefore inaccurate. Eyal: That is correct. A part of the SharePlex product goes back to the source database and completes the missing information. This is done only for certain types of Update statements but is not nessasery for Inserts and Deletes. 2) Reading the redo log is not a supported interface. From the very beginning, Oracle has changed redo log formats to support functional enhancements. We must therefore reserve the right to continue to make needed log format changes. For this reason, certification of any third party product using this interface is not possible. Since this is an unsupported interface, the accuracy or completeness of the data in the destination database can not be assured. Eyal: The power of the product is the direct result from reading the raw log data. It is our core competency in Quest to understand and support the changing nature of the Oracle log. The reality is that between version 7.0 until 8.1.6 there where only minor changes to the log. Since we are a close partner with Oracle we get early releases of the software and we have the chance to update the product as needed. So far this has never been an issue since most large production sites are running Oracle versions that are atleast 6 months to a year old. Regarding assurance to the completeness of the data, we do not expect Oracle to provide any assurance. Quest is the one that assures the content of the destination. Quest support has some of the best support experts in the business. Any problem with the database content should be directed to our support organization and not Oracle World Wide Support. Likelihood of Occurrence ~ Unknown. However, even a low likelihood is a concern for disaster recovery (DR). In disaster failovers, the remote server's database may be the only viable copy. Eyal:
