Is it the OS or the JVM or the JDBC Driver

Question

Hello All,
I have about 25 different databases I want hit with the application depending on who the user is. I am using DriverManager.getConnection or Datasource.getConnection to obtain connection to the database.
It is not connection pool so all the connections and datasources are configured with in the application.
The problem I am facing is I cannot connect to some of the Databases at certain time and is always random, and If I try to run it as a stand alone Java application, I can connect to the data base fine.
So after doing much research and calling IBM, in order to recreate the problem, I tried to run a simple java program in a loop , see if I can connect all of them on work station. There also I ran into the same issue. Connecting to database was really random. After looking at the JDBC debug output and every thing, I found an intersting issue.
When the JDBC connects to the database on my workstation, i don't see the netstat activity to that database. If I just run the program for that one database, I can connect oaky.
I tried everything, allowing TCP to have more ports, connection time outs, I also used the IP's instead of host names to avoid nslookup issues. Synchronizing the method that connects to database, nothing seem to improve my chances
Is it JVM related or Operating system or the JDBC, I couldn't tell. I tried using lot of Memory just to make sure it is not GC or resource issue, without any chance
Anyone with input is much appreciated.
I appreciate your help in advance.

Answer 1

All the Databases are of type Informix.
Probably I picked wrong words when I said stand alone. I am actually using in servlet where I am facing the problem. To be precise when I tried to recreate the problem , all I did is I created a java program which connects to all the database one at a time in a loop and does a simple query and exists out, and closes everything.
I have another program which just runs for only one database.
So If I take the database which fails in the loop and run it on the other one it just connects fine and everything.
About the connection issue all I have is just one connection per database, after I am done, I just close it and the connection to database is attempted.
Following is the program which runs through all the databases, I have changed few things to post it on the forum.
public class InformixAll {
     volatile static IfxDataSource ds;
     public static void main(String[] args) {
          String[] dbArray =
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
                    "1.1.1.1",
          try {
               ds = new IfxDataSource();
          } catch (SQLException e1) {
               e1.printStackTrace();
          for (int i = 0; i < dbArray.length; i++) {               
               doIt(dbArray, i);
     public synchronized static void doIt(String dbArray, int i) {
                              String ip = null;
               try {
                         Process p = Runtime.getRuntime().exec("nslookup " + dbArray);
                         BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
                         String k = null;
                         while ((k = reader.readLine()) != null) {
                              if(k.indexOf(dbArray) > 1)
                              {k = reader.readLine();
                                   System.out.println(k);
                                   ip =k.trim();
                    } catch (Exception e) {
                         e.printStackTrace();
               try {
                    ds.setDatabaseName("SOME DB");
                    ds.setServerName("DEMO");
                    ds.setPortNumber(100);
                    ds.setUser("USER");
                    ds.setPassword("PASS");
                    ds.setIfxIFXHOST(ip);
                    ds.setIfxIFX_ISOLATION_LEVEL("1");
                    ds.setIfxINFORMIXCONRETRY(50);
                    ds.setIfxINFORMIXCONTIME(3);
                    ds.setIfxTRACE(3);
                    ds.setIfxTRACEFILE("c:\\temp\\isptrace.txt");
                    ds.setIfxPROTOCOLTRACE(2);
                    ds.setIfxPROTOCOLTRACEFILE("c:\\temp\\prot.txt");
                    ds.setIfxIFX_AUTOFREE(true);
                    ds.setIfxOPTOFC("1");
                    ds.setIfxIFX_ISOLATION_LEVEL("1");
                    Connection c = ds.getConnection();
                    PreparedStatement st = c.prepareStatement(" SELECT * FROM TABLE ");
                    ResultSet rs = st.executeQuery();
                    System.out.print(i + "." + " Number " + dbArray + " = ");
                    if (rs.next()) {
                         System.out.print(" OKAY ");
                    } else {
                         System.out.print(" OKAY ");
                    System.out.println();
                    rs.close();
                    st.close();
                    c.close();
               } catch (SQLException e) {
                    System.out.println("Could not Connect to " + dbArray);