You do not need to use multiple SQLCAs to connect to more than one database or have more than one connection to a single database.
Each SQLCA can have one unnamed connection. Each SQLCA has an active or current connection See SET CONNECTION statement [Interactive SQL] [ESQL].
All operations on a given database connection must use the same SQLCA that was used when the connection was established.
Operations on different connections are subject to the normal record locking mechanisms and may cause each other to block and possibly to deadlock. For information about locking, see Using Transactions and Isolation Levels.