The optimization process and recommendations:

1. Avoid Calling Functions With Indexed Columns (query line: 31): When a function is used directly on an indexed column, the database's optimizer won’t be able to use the index. For example, if the column `sysdate` is indexed, the index won’t be used as it’s wrapped with the function `last_day`. If you can’t find an alternative condition that won’t use a function call, a possible solution is to store the required value in a new indexed column.

The optimized query:

SELECT
        atx.journal_id,
        ab.c_date 
    FROM
        acct_batch ab 
    JOIN
        acct_tx atx 
            ON ab.acct_id = atx.acct_id 
            AND ab.batch_id = atx.batch_id 
    JOIN
        journal j 
            ON j.journal_id = atx.journal_id 
            AND j.journal_type_id = 6 
    JOIN
        acct a 
            ON a.acct_id = atx.acct_id 
            AND a.acct_type_id = 32 
    JOIN
        payments p 
            ON p.payment_id = j.payment_id 
    JOIN
        routing r 
            ON r.route_id = p.route_id 
            AND r.acq_code = 'RZ_NS' 
    JOIN
        acq_acct aa 
            ON aa.acq_code = r.acq_code 
            AND aa.acq_acct_code = r.acq_acct_code 
            AND aa.slc = 'MXM' 
    WHERE
        ab.c_date BETWEEN to_date(to_char('01-JUL-2015')) AND last_day(sysdate)