Why in 10G, when you use real time apply feature in conjunction with Maximum Protection, you can achive zero data loss, but not zero database downtime??

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Sharda

  • Aug 23rd, 2006
 

In Data Guard , Maximum Protection mode offers the highest level of data protection. Data is synchronously transmitted to the standby database from the primary database and transactions are not committed on the primary database unless the redo data is available on at least one standby database configured in this mode. If the last standby database configured in this mode becomes unavailable, processing stops on the primary database. This mode ensures no-data-loss. But it can not guarantee zero down time ..as ..if a standby database becomes unavailable (for example, because of network connectivity problems), procession stops at primary database.

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smushti

  • Sep 10th, 2006
 

When you say "If the last standby database configured in this mode becomes unavailable, processing stops on the primary database. " does 'processing stops' mean committing a transaction stops on the primary database...if so, there is data loss correct?

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senthil kumaravel

  • Oct 16th, 2006
 

Since the primary database will be shutdown automatically incase of the transaction is not able to processed in atleast one standby database, all UNCOMMITTED transaction will be rolled back.  Since, the transaction is not commited yet in primary database, there will not be any change in the data - no data loss.  So the transaction is not completed and it has been rolled back.

If there is no transaction commited there there is no-data-loss.

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senthilora

  • Sep 24th, 2007
 

Maximum Protection mode - guarantees Zero data loss.  But it can not guarantee Zero down time.

Any transaction happening in Primary Database has to be propagated and commited in Standby Database.  That means, COMMIT get completes only after the COMMIT has been performed in both PRIMARY and STANDBY.

If, for any reason, the transaction was performed carried out in STANDBY, the primary database will be SHUTDOWNED (without COMMITING the current transaction).

This gurantees Zero data loss - as all the COMMITED transactions will be available in STANDBY.

UNCOMMITED transactions - are failed transactions and so there should not be any change in the data - Zero data loss.



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