You also learn how the datatype is an ordered group of elements, all of the same type.It is a general concept that encompasses lists, arrays, and other familiar datatypes.
Please drop the index on the column before you update the table. Check the row count which matches with the Predicate in where clause. of rows in the table then supress use of index on the columns used in predicate of where clause.
If the field is not part of an index, I suspect your query is doing a table scan.
Do an explain plan and see where Oracle is spending most of it's effort.
But I do not be a non-partitioned table can take advantage of parallel insert or update statement.
I suspect though that you query may be doing a full table scan. It may go quicker if the Oracle can identify the rows through an index scan.
If a FTS is part of the plan, then look at your predicates.Do an explain plan and see where Oracle is spending most of it's effort.If the rows can be identified by an index scan the update should go alot quicker.You could also do: create table tab2 as select case when then 'abc'