Isolation Level 2 or 20 

If isolation level 2 or 20 (repeatable) is specified, shared locks are requested for all the tables addressed by an SQL statement data query before processing starts.

When an sql statement generates a result table that is not physically stored, these locks are not released until the end of the transaction or until the result table is closed. Otherwise, they are released immediately after the sql statement has been processed. This table shared lock is not assigned to the transaction in the case of SQL statements in which just one table row is processed that is determined by key specifications or by CURRENT OF <result_table_name>.

In addition, an implicit shared lock is assigned to the transaction for each row read while an sql statement is being processed. These locks can only be released with the UNLOCK statement or by ending the transaction.

When rows are inserted, updated or deleted, exclusive locks are assigned implicitly to the transaction for the rows concerned. These cannot be released until the end of the transaction. However, no locks are set for the entire table.