You have created some materialized views to improve the performance of several queries. Which four must be true to enable sessions to benefit from improved response time made possible by these…

Question

Options

• AQuery rewrite must be enabled for the sessions.
• BBitmap indexes must exist on all the columns involved in the join operations for the defining query
• CAll or part of the query results must be obtainable from one or more MVIEWs.
• DBitmap join indexes must exist on all the columns involved in the join operations.
• ESession users must have query rewrite privilege.
• FThe MVIEWs must be enabled for query rewrite.
• GAll or part of the query results must be obtainable from one MVIEW.

• A
  79% (30)
• D
  13% (5)
• E
  3% (1)
• G
  5% (2)

Explanation

A: For a given user's session, ALTER SESSION can be used to disable or enable query rewrite for that session only. B: Bitmap indexes on the join columns would improve performance. C (not G) : One of the major benefits of creating and maintaining materialized views is the ability to take advantage of query rewrite, which transforms a SQL statement expressed in terms of tables or views into a statement accessing one or more materialized views that are defined on the detail tables. * A materialized view is only eligible for query rewrite if the ENABLE QUERY REWRITE clause has been specified, either initially when the materialized view was first created or subsequently with an ALTER MATERIALIZED VIEW statement. * Enabling or disabling query rewrite: by the CREATE or ALTER statement for individual materialized views by the initialization parameter QUERY_REWRITE_ENABLED by the REWRITE and NOREWRITE hints in SQL statements * A materialized view is a replica of a target master from a single point in time. The master can be either a master table at a master site or a master materialized view at a materialized view site. Whereas in multimaster replication tables are continuously updated by other master sites, materialized views are updated from one or more masters through individual batch updates, known as a refreshes, from a single master site or master materialized view site.

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