PORTAL password is used when upgrade/patch portal schema. We got 2 ways to get / set , either by oiadmin or ldap*** command.
For Portal 10.1.4.x. We can run command to get /set password, well, works for other PORTAL attributes.
ldapsearch -h <host> -p <port> -D cn=orcladmin -w <password> -b "cn=IAS,cn=Products,cn=OracleContext" -s sub -v OrclresourceName=PORTAL| grep orclpasswordattribute
ldapmodify is for set password of course.
Note: for old Portal version 9.x and 10.1.2.x , it is good idea to call oidadmin and it launch GUI tool for you.
More details can be seen in "How to get the Portal Schema Password of the Infrastructure database [ID 198800.1]"