Signals that you want to use the lock mechanisms of SQL for
    consistency in data retrieval and update. Read/write is the
    default transaction. Use the read/write transaction mode when
    you need to:

    o  Insert, update, or delete data

    o  Retrieve data that is guaranteed to be correct at the moment
       of retrieval

    o  Use SQL data definition statements

    When you are reading a row in a read/write transaction, no other
    user can update that row. Under some circumstances, SQL may lock
    rows that you are not explicitly reading.

    o  If your query is scanning a table without using an index, SQL
       locks all the rows in the record stream to maintain isolation
       level serializable.

    o  If your query uses indexes, SQL may lock part of an index,
       which has the effect of locking several rows.