## Derby Network Server sample program

The Network Server sample demo program (NsSample) is a simple JDBC application that interacts with the Derby Network Server. The program:

1. Starts the Derby Network Server.
2. Connects to the Network Server and creates the database if not already created. The Network Client driver is loaded automatically.
3. Checks to see if the schema is already created, and if not,
4. Creates the schema, which includes the `SAMPLETBL` table and corresponding indexes.
5. Connects to the database.
6. Loads the schema by inserting data.
7. Starts client threads to perform database related operations.
8. Has each of the clients perform DML operations (select, insert, delete, update) using JDBC calls; in particular, one client opens an embedded connection to perform database operations, while the other client opens a client connection to the Derby Network Server to perform database operations.
9. Waits for the client threads to finish the tasks.
10. Shuts down the Derby Network Server at the end of the demo.

The following files in the `DERBY_INSTALL\demo\programs\nserverdemo\` directory are needed to run the sample program (DERBY_INSTALL is the directory where you installed Derby):

- `NsSample.java`
  This is the entry point into the demo application. The program starts up two clients. One client opens an embedded connection to perform database operations, while the other client opens a client connection to the Derby Network Server to perform database operations. This program provides the following constants that can be changed to modify the sample demo:
  - `NUM_ROWS` - The number of rows that must be initially loaded into the schema.
  - `ITERATIONS` - The number of iterations for which each client thread does database related work.
  - `NUM_CLIENT_THREADS` - The number of clients that you want to run the program against.
  - `NETWORKSERVER_PORT` - The port on which the network server is running.
  You can also modify the program to exclude starting the Network Server as part of the sample program. Make sure to recompile the Java files before running the program if you make any changes to the source code.
- `NsSampleClientThread.java` This file contains two Java classes:
  - The `NsSampleClientThread` class extends Thread and does all the necessary work by instantiating a `NsSampleWork` instance.
  - The `NsSampleWork` class contains everything required to perform DML operations using JDBC calls. The `doWork` method in the `NsSampleWork` class represents all the work done as part of this sample program.
- `NetworkServerUtil.java`
  This file contains helper methods to start the Derby Network Server and to shut down the server.
- Compiled class files:
  - `NsSample.class`
  - `NsSampleClientThread.class`
  - `NetworkServerUtil.class`

## Running the Network Server demo program

To run the Derby Network Server demonstration program:

1. Open a command prompt and change directories to the `DERBY_INSTALL\demo\programs\` directory.
2. Set the CLASSPATH to the current directory (".") and also include the following jar files in order to use the Derby Network Server and the Derby Client Network JDBC Driver.
   - `derbynet.jar`
     The Network Server jar file. It must be in your CLASSPATH to use any of the Derby Network Server functions.
   - `derbyclient.jar`
     This jar file must be in your CLASSPATH to use the Derby Client Network JDBC Driver.
   - `derby.jar`
     The Derby database engine jar file.
3. Test the CLASSPATH settings by running the following java command:

       java org.apache.derby.tools.sysinfo

   This command will show the Derby jar files that are in the CLASSPATH along with their respective versions.
4. Once you have set up your environment correctly, execute the application from the
   `DERBY_INSTALL\demo\programs\` directory:

       java nserverdemo.NsSample [driverType]

   - Where the possible values for driverType are:
     - derbyClient (default)

You should receive output similar to the following if the program runs successfully:
`Using JDBC driver: org.apache.derby.jdbc.ClientDriver
Derby Network Server created
Apache Derby Network Server started and ready to accept connections on port 1621
[NsSample] Derby Network Server started.
[NsSample] Sample Derby Network Server program demo starting.
Please wait .....................
[NsSampleWork] Begin creating table - SAMPLETBL and necessary indexes.
[NsSampleClientThread] Thread id - 2; started.
[NsSampleWork] Thread id - 2; requests database connection, dbUrl =jdbc:derby://localhost:1621/NSSampledb;create=true;
[NsSampleClientThread] Thread id - 1; started.
[NsSampleWork] Thread id - 1; requests database connection, dbUrl =jdbc:derby:NSSampledb;
[NsSampleWork] Thread id - 1; inserted 1 row.
[NsSampleWork] Thread id - 1; inserted 1 row.
[NsSampleWork] Thread id - 1; deleted 1 row with t_key = 9372
[NsSampleWork] Thread id - 1 selected 1 row [920,Derby50 ,951.7808,9216]
[NsSampleWork] Thread id - 1 selected 1 row [920,Derby50 ,951.7808,9216]
[NsSampleWork] Thread id - 1; inserted 1 row.
[NsSampleWork] Thread id - 1 selected 1 row [920,Derby50 ,951.7808,9216]
[NsSampleWork] Thread id - 1; deleted 1 row with t_key = 9216
[NsSampleWork] Thread id - 1 selected 1 row [824,Derby26 ,8.802546E22,9155]
[NsSampleWork] Thread id - 1; updated 1 row with t_key = 9155
[NsSampleWork] Thread id - 1; closed connection to the database.
[NsSampleClientThread] Thread id - 1; finished all tasks.
[NsSampleWork] Thread id - 2; updated 0 row with t_key = 9372
[NsSampleWork] Thread id - 2; updated 1 row with t_key = 9155
[NsSampleWork] Thread id - 2 selected 1 row [56,Derby26 ,8.802546E22,9155]
[NsSampleWork] Thread id - 2; inserted 1 row.
[NsSampleWork] Thread id - 2; updated 1 row with t_key = 9155
[NsSampleWork] Thread id - 2; deleted 1 row with t_key = 9155
[NsSampleWork] Thread id - 2 selected 1 row [785,Derby2 ,0.30170244,8280]
[NsSampleWork] Thread id - 2 selected 1 row [785,Derby2 ,0.30170244,8280]
[NsSampleWork] Thread id - 2; updated 1 row with t_key = 8280
[NsSampleWork] Thread id - 2 selected 1 row [59,Derby2 ,0.30170244,8280]
[NsSampleWork] Thread id - 2; closed connection to the database.
[NsSampleClientThread] Thread id - 2; finished all tasks.
[NsSample] Shutting down network server.
Apache Derby Network Server - shutdown
[NsSample] End of Network server demo.
`

Running the demo program will also create new directories and files:

- `NSSampledb`
  This directory makes up the NSSampledb database.
- `derby.log`
  This log file contains Derby progress and error messages.