If you want to pass a notification message or success message to a next page by using URL redirect, you just need to concatenate below strings to the end of your URL ( ¬ification_msg=[your message]/[message checksum]/ )
(If you use branch it simply happens if you click “include process success message”.)
Example PL/SQL code:
v_NOT_FOUND_TICKET_MSG varchar2(512) := 'App+can+not+get+this+ticket+information+from+XXXX!+This+information+may+not+be+up+to+date.';
v_URL := v_URL || '¬ification_msg=' || v_NOT_FOUND_TICKET_MSG || '/' || WWV_FLOW_UTILITIES.LOV_CHECKSUM(v_NOT_FOUND_TICKET_MSG) || '/';
WWV_FLOW_UTILITIES.LOV_CHECKSUM is an internal function that generates an MD5 after removing special characters and adding application Salt. (APEX for some usage create Salt from IP by HEXTORAW(L_SESSION_REC.IP_ADDRESS) and some time from Application Alias). GET_PAGE_CHECKSUM also is quite similar with some additional Salt concatenated like page number and the request.
Example URL: (%2F is equal to / which is a URL encode APEX automatically does):
Note: in URL encoding we replace space with +