The reason to trace the CBO is to understand why the Optimizer made some decisions. In this example we are going to see why same query sometimes uses an index and others it doesn’t, same example was explained HERE It is always useful to have a “GOOD” and “BAD” execution, this way it is easier... » read more
You might face this question if you are going though job interviews. and these are some cases where the Optimizer thinks going for a full table scan is better than index scan. 1:- The selectivity of the records is very high: We have this table and range of contents: We have an index and it... » read more
On this activity we are going to generate snapshots on an active standby so we can be able to create AWR reports. This is our setup: We need to perform the following steps to enable AWR reporting from a physical standby database. 1:- Unlock SYS$UMF user and reset the password. SYS$UMF account is used to... » read more