Dropping large columns in database - ORACLE
alter table table_name set unused There may be a situation where you want to drop a column that has a huge data 10 Million rows .It will take lot of time to drop that column and the worst part is that Oracle will place a lock on that tables until With the " alter table set unused " command you can make that column invisible to users. at a later point of time. when you set the column to unused it will be stored in sys as unused. MARKING UNUSED COLUMN sql> desc abc_test Name Null Type ---------- ---- ------------ NAME VARCHAR2(20) TOTAL_ROWS NUMBER ...