Buffer busy wait happens when a session wants to access a database block in the buffer cache but it cannot as the buffer is “busy”. The two main cases where this can occur are: Another session is reading the block into the buffer Another session holds the buffer in an incompatible mode to our request…
There can be several situations where you want to test the impact of dropping a column from a table, till 11gR2 Oracle provided an option to mark a column as UNUSED before dropping a column, and do ALTER TABLE … DROP UNUSED COLUMNS at a later time but marking a column UNUSED is a irreversible…
With 12cR1 you can now move table partitions and sub-partitions online. There are lot of reasons for which you might want to move a table partition or sub-partition such as:- Re-cluster data and reduce fragmentation. Move a partition to another tablespace. Modify create-time attributes. Store the data in compressed format using table compression. The problem…
Oracle Database Internal Mechanism 