To connect to a PDB, you have to use the service name of the pluggable database. But what when there is an older legacy application that can only use an SID to connect to a database? And what if we just migrated an older legacy database to a PDB? When starting the application, you might see something like:
ORA-12505: TNS:listener does not currently know of SID given in connect descriptor
There is a parameter called
USE_SID_AS_SERVICE_listener that can be used to tell the listener to handle SIDs like service names. So the listener will interpret the SID given in the connection as a service name and will then connect you to the database.