With DISCONNECT

Go Up to Closing a Database

To close all open databases by disconnecting from them, use the following DISCONNECT syntax:

EXEC SQL
DISCONNECT {ALL | DEFAULT};

For example, each of the following statements closes all open databases in a
program:

EXEC SQL
DISCONNECT ALL;
EXEC SQL
DISCONNECT DEFAULT;

To close specific databases, specify their handles as comma-delimited parameters, using the following syntax:

EXEC SQL
DISCONNECT handle [, handle ...];

For example, the following statement disconnects from two databases:

EXEC SQL
DISCONNECT DB1, DB2;

Note: A database should not be closed until all transactions are finished with it, or it must be reopened and its resources reallocated.