Thank you Sundar,
I know that documentation and had already tried secondary connection, the problem is the only type of secondary connection which is supported is a service connection to the same Netweaver database, this is used only for executing the stored procedure in a different LUW than the Netweaver transaction.
If you create a secondary connection on DBCON and pass the connection name to connection parameter you get an error, if you pass "R/3*connectionName" there's no error but queries return no data from tables present in the schema of the user declared for connectionName on DBCON.
In my use case I don't need to access more than one schema during the same execution of the stored procedure but on different executions of it.
Thank you
Best regards