"The PGA memory used for the ORA-04036 instance has exceeded PGA_AGGREGATE_LIMIT" has occurred.

After upgrading Oracle version 12.1.0.2.0 to 19.3.0.0.0

"The PGA memory used for the ORA-04036 instance has exceeded PGA_AGGREGATE_LIMIT" has occurred.

If you execute "SELECT * FROM v $ process" regularly and follow up,

The value of PGA_USED_MEM for the bag ground process PNAME = Mnnn (thread of MMON) is continuously increasing.

The value of PGA_USED_MEM for the bag ground process PNAME = Wnnn (thread of WMON) is also continuously increasing.

(example)

PNAMEPGA_USED_MEM (June 6th) PGA_USED_MEM (July 1st)

M00　138,206,697⇒163,817,097

W00　13,635,681⇒49,269,033

If you restart the instance before the PGA memory exceeds PGA_AGGREGATE_LIMIT,

The value of PGA_USED_MEM will decrease once, but then continue to increase again.