By default SharePlex is using the BEQ protocol connecting to the database. If you want to change this to use your Shared Server setup, you will have to rerun ora_setup.
1. Shutdown SharePlex
2. Run ora_setup and append to the system and SharePlex user password the string "@Shared_TNS_ALIAS" for example: system/manager@hd920 and splex/splex@hd920
3. WINDOWS ONLY: edit the paramdb and comment the shorter entry of SP_ORD_LOGIN_O.ORACLE_SID out
4. Start SharePlex
Starting with SharePlex 8.6.2, it is no longer required to append the password with the connect string in SQL*net environment. During running of ora_setup, SharePlex is able to gather info on connect string and is able to append the value of connect string to the password field specified by the user. Please refer to the knowledgebase article 184662 for details.