Oracle SQL: Calculate MEMORY_TARGET out of 10g database

memory_target = sga_target + max(pga_aggregate_target, maximum PGA allocated)

SELECT TRUNC (SUM (VALUE) / 1024 / 1024) || ' MB' memory_target
FROM (SELECT TO_NUMBER (VALUE) VALUE
FROM v$parameter
WHERE name = 'sga_target'
UNION ALL
SELECT MAX (VALUE) VALUE
FROM (SELECT TO_NUMBER (VALUE) VALUE
FROM v$parameter
WHERE name = 'pga_aggregate_target'
UNION ALL
SELECT TO_NUMBER (VALUE) VALUE
FROM v$pgastat
WHERE name = 'maximum PGA allocated'));