You don't need to worry about locks in Teradata, TD automatically place appropriate mode of lock on tables or other database objects. In your case, it'll place WRITE lock on the table TBL2. Other users can read the table data through ACCESS mode lock, but not through READ lock.
Pawan is right - TBL2 gets a write lock. If a user accesses the table, he will normally aquire a read lock, so will be delayed until the write lock is released. (This can be avoided by setting the NOWAIT option in bteq - other tools usually have equivalent options - in which case the command is rejected with table not available.) If the user specifies LOCKING FOR ACCESS, he can read through the write lock, but will get the rows currently in the table, so could get any number of rows.