What is the difference between unused and invisible column?
We are going to drop 4 columns from a large table. Size of table is 6 GB and it has 60 million records.
It takes 17 minutes using alter table MyTable drop (column1, column2, column3, column4);
But that generates huge amounts of REDO and we are looking for more gentle and quicker way to drop these columns.
By setting the columns to unused or invisible, we can drop the columns one by one at a later stage.
======================================================
select * from v$version;
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE 12.1.0.2.0 Production
TNS for Linux: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production