Sample code below:
<db:stored-procedure doc:name="Call Stored procedure - myStoredProc"
doc:id="73d4a90e-29bf-4be1-8e91-5c61a536fe39"
config-ref="DB_Connection_Config_Ref">
<db:sql >{ call myStoredProc (:P_FIRST_NAME, :P_LAST_NAME) }</db:sql>
<db:parameter-types>
<db:parameter-type key="P_FIRST_NAME" type="NVARCHAR" />
<db:parameter-type key="P_LAST_NAME" type="NVARCHAR" />
</db:parameter-types>
<db:input-parameters><![CDATA[#[%dw 2.0
output application/java
---
{
P_FIRST_NAME: payload.firstName,
P_LAST_NAME: payload.lastName
}]]]></db:input-parameters>
</db:stored-procedure>