Oracle 19c - DDL and locking

Hello

We have a question on the DDL and its resultant locking mechanism. Just trying to make sure we understand this

Lets suppose we have a table and session # 1 perform an alter table operation to add or modify column. The table could have either 10K or 200K rows

Based on our understanding, this will acquire an exclusive implicit lock on that table for the duration of the time it takes to complete the alter table statement

Correct?

Now while that alter has not been completed, session # 2 try to perform a DML operation so that session # 2 will not be able to do that unless and until session # 1 is done altering the table. Correct?