The "ORA-01000: maximum open cursors exceeded" error when using an Oracle database for PAM will occur whenever Oracle runs out of open cursors. PAM 4.2 does use more open cursors than 4.1 so it is possible thatr after upgrading to 4.2 you may see this error.
A cursor is a pointer to a private SQL area that stores information about the processing of a SELECT or data manipulation language (DML) statement (INSERT, UPDATE, DELETE, or MERGE). Cursor management of DML statements is handled by Oracle Database.
To resolve this issue you will need to increase the number of open cursors available on your Oracle database. Please discuss this with your DBA. Please see the below Oracle docs for your reference:
How to increase the OPEN_CURSOR in Oracle:
Once the open_cursors is set (i.e., open_cursors=1500) please restart PAM. Thank you.