How to check PGA target advice in Oracle

V$PGA_TARGET_ADVICE simulates different PGA target sizes and reports the predicted cache hit percentage and overallocation count. Aim for the size where cache_hit_perc approaches 100 and estd_overalloc_count drops to 0.

SELECT ROUND(pga_target_for_estimate / 1024 / 1024) AS target_mb,
       estd_pga_cache_hit_percentage              AS cache_hit_perc,
       estd_overalloc_count
FROM   v$pga_target_advice;