Perform a fast refresh - Oracle Replication

Q.  What needs to be done to perform a fast refresh?
- Published on 30 Jul 15

a. The server that manages the snapshot executes the snapshot's defining query
b. Query should replace the existing snapshot data to refresh the snapshot
c. The server that manages the snapshot first identifies the changes that occurred in the master since the most recent refresh of the snapshot and then applies them to the snapshot
d. Create a snapshot log for the table so that fast refreshes of the snapshots are an option

ANSWER: The server that manages the snapshot first identifies the changes that occurred in the master since the most recent refresh of the snapshot and then applies them to the snapshot

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    Discussion

  • Nirja Shah   -Posted on 18 Sep 15
    - The data that a snapshot presents does not necessarily match the current data of its master tables.

    - A table snapshot is a transaction-consistent reflection of its master data as that data existed at a specific point in time.

    - Oracle can refresh an individual snapshot using either a complete refresh or a fast refresh.

    - Complete Refreshes
    - To perform a complete refresh of a snapshot, the server that manages the snapshot executes the snapshot's defining query.
    - The result set of the query replaces the existing snapshot data to refresh the snapshot.
    - Oracle can perform a complete refresh for any snapshot.

    - Fast Refreshes
    - To perform a fast refresh, the server that manages the snapshot first identifies the changes that took place in the master since the most recent refresh of the snapshot and then applies them to the snapshot.
    - Fast refreshes are more efficient than complete refreshes when there are few changes to the master because participating servers and networks must replicate less data.
    - Fast refreshes are available for snapshots only when the master table has a snapshot log.

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