Why log or not a materializad view ?

Question

Hi,
I know we can log a materialized view but not found a reason to do it. I'm not talking about materilized view logs used to refresh a mv but to log a mv.
If I work with two databases (a - master and b - mv site) and do a lot of changes to a table on database a replicated on database b. Changes are logged on both sides and to my opinion wasting space on database b. Case 2, if do a complete refresh the deleted and inserted data will be logged using sometimes a lot of disk space.
Why my question, I'm used to turn off logs on materilized views but now I'm working with some databases as and want to propose not to log mv because it's usual to have disk space problems.
What do you think about ?

Answer 1

What, exactly, do you mean by "log a materialized view" if not the presence of materialized view logs? Are you talking about
CREATE MATERIALIZED VIEW
  LOGGING | NOLOGGINGIf so, that merely controls whether direct-path inserts to the materialized view or the initial materialized view creation generates redo. If you are doing incremental refreshes, NOLOGGING is irrelevant because the refresh mechanism doesn't use direct-path operations. If there are any indexes on the materialized view, NOLOGGING is less relevant because index operations are always logged, so you lose most of the performance benefits.
If you are doing complete refreshes of materialized views and those materialized views are not in refresh groups, Oracle will do direct-path loads and NOLOGGING can be quite useful assuming there are no indexes. There are obviously downsides from a recovery standpoint, however, since those are unrecoverable operations. It may also be useful when initially building a large materialized view to use NOLOGGING.
Justin