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The disadvantages section of the Wikipedia entry for Oracle Data Guard says:

If the network link connecting primary and standby is over-subscribed, the redo logs are not applied in chronological order

Is this true? I can't find a reference to this in the Oracle documentation.

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that is nonsense. I think he wanted to write "..., the redo logs are not transfered in chronological order" –  miracle173 Aug 26 '13 at 11:54

3 Answers 3

I simply do not believe. It's impossible. There is process called FAL (Fetch Archive Log), it can happen that redo-logs are not TRANSFERRED in chronological order, but anyway they must be APPLIED in chronological order.

Also logical standby has can have some gotchas but those are not related to network link. (For example for some reason LOCK TABLE statement is not propagated to slave)

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What can happen is this:

You have the standby database in READ ONLY mode and the primary is generating new archives. The archives are archived locally and remote, if possible.

A remote destination can be optional.

It could very well be that in some time interval the standby site is not receiving all archives and in a later interval it is receiving them again. The FAL client will fetch the gaps during the recovery of the standby database and doing so, it will automatically solve this problem for you. This is also a reason not to remove archives from the primary site, until you know absolutely for sure that they are OK on the remote site.

For me the only way to know they are OK is when they have been successfully applied on the standby.

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That entry is wrong. He should typed 'shipped' instead 'applied'.

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