I connect to db2 use jdbc ,the programe is :

try{
Class.forName("COM.ibm.db2.jdbc.app.DB2Driver");
Connection db = DriverManager.getConnection("jdbc:db2:dl","db2inst 1","db2inst1");
Statement stmt = db.createStatement();
System.out.println("11111111111111");
Connection db_exec = DriverManager.getConnection("jdbc:db2:dl","db2inst 1","db2inst1");
System.out.println("22222222222222");
Statement ppstmt = db_exec.createStatement();

........


the result of run is :

$ java ImChangeData 3 Dj
11111111111111
[IBM][CLI Driver] SQL1224N A database agent could not be started to service a request, or was terminated as a result of a database system shutdown or a force command. SQLSTATE=55032

or the instance crashed (see db2diag.log) or you have been forced by system
should give -911
check diaglog on server or activate local trace in db2cli.ini... and see details

...or the maximum number of agents has been reached...
...or it was a personal edition that only allows one connection at a time...

I check all about you say ,and this programe had run in another system ,but now it can't run.I don't know why.

I change then programe:
try{
Class.forName("COM.ibm.db2.jdbc.app.DB2Driver");
Connection db = DriverManager.getConnection("jdbc:db2:dl","db2inst 1","db2inst1");
Statement stmt = db.createStatement();
System.out.println("11111111111111");
//Connection db_exec = DriverManager.getConnection("jdbc:db2:dl","db2inst 1","db2inst1");
System.out.println("22222222222222");
Statement ppstmt = db.createStatement();

then it's ok