This article looks at the range of client access mechanisms for Windows that can be used with the Recital C-ISAM Bridge and details bridge configuration and usage.

Overview

Just because the format of data is regarded as 'legacy' does not make that data in any way obsolete. Modern client interfaces can not only extend the life of long-term data, but also provide different ways to analyse and gain advantage from that data.

Recital Corporation provides a range of solutions to interface to Informix compliant C-ISAM data on Linux or UNIX from Windows clients.

.NET

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Fig 1: Recital Mirage .NET application accessing the C-ISAM Demo table.

Recital offers two alternative ways to access C-ISAM data using Microsoft .NET:

The Recital .NET Data Provider is a managed Data Provider written in C# that provides full compatibility with the Microsoft SQLserver and OLE DB data providers that ship with the .NET framework. It is fully integrated with the Visual Studio .NET IDE supporting data binding and automatic code generation using the form designer. The Recital .NET Data Provider works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.

Recital Mirage .NET is a complete solution for migrating, developing and deploying 4GL database applications. Recital Mirage .NET works in conjunction with the Recital Mirage .NET Application Server for Linux or UNIX to access C-ISAM data.

JDBC

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Fig 2: Java™ Swing JTable accessing the C-ISAM Demo table via the Recital JDBC Driver.

The Recital JDBC Driver is an all Java Type 4 JDBC 3.0 Driver, allowing you to access C-ISAM data from Java applets and applications. The Recital JDBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.

ODBC

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Fig 3: Microsoft® Office Excel 2003 Pivot Chart and Pivot Table accessing the C-ISAM Demo table via the Recital ODBC Driver.

The Recital ODBC Driver is an ODBC 3.0 Driver, allowing you to access C-ISAM data from your preferred ODBC based Windows applications. You can develop your own applications in languages such as C++ or Visual Basic, manipulate the data in a spreadsheet package or word processor document and design charts, graphs and reports. The Recital ODBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.

Configuring the Recital C-ISAM Bridge

Data access is achieved through a C-ISAM Bridge.  This requires the creation of an empty Recital table that has the same structure as the C-ISAM file and of a RecitalC-ISAM Bridge file.

On Linux and UNIX, Recital Terminal Developer and the Recital Database Server come complete with an example C-ISAM data file, C-ISAM index and Recital C-ISAM bridge that can be used for testing and as a template for configuring your own C-ISAM bridges.  The Recital Database Server also includes a bridge creation ini file.

Step 1:

Create a Recital table with the same structure as the C-ISAM file.  The fields/columns in the structure file must exactly match the data type and length of those in the C-ISAM file.  The Recital table will have one byte more in total record length due to the Recital record deletion marker.

To create the table, use the SQL CREATE TABLE command or the Recital Terminal Developer CREATE worksurface.  The SQL CREATE TABLE command can be called directly:

SQLExecDirect:
  In:      hstmt = 0x00761BE8,
    szSqlStr = "CREATE TABLE cisamdemo.str (DD Char(4)
              DESCRIPTION "Dd...", cbSqlStr = -3
  Return:  SQL_SUCCESS=0

or be included in a 4GL program:

// createtab.prg
CREATE TABLE cisamdemo.str;
    (DD Char(4) DESCRIPTION "Dd",;
     CONFIRM Char(6) DESCRIPTION "Confirm",;
     PROCDATE Char(6) DESCRIPTION "Procdate",;
     CONTROL Char(5) DESCRIPTION "Control",;
     DOLLARS Decimal(13,2) DESCRIPTION "Dollars",;
     DEALER Char(5) DESCRIPTION "Dealer",;
     TERRITORY Char(2) DESCRIPTION "Territory",;
     WOREP Char(12) DESCRIPTION "Worep",;
     CURRTRAN Char(3) DESCRIPTION "Currtran",;
     TRADDATE Char(6) DESCRIPTION "Traddate",;
     CITY Char(10) DESCRIPTION "City",;
     ACCOUNT Char(11) DESCRIPTION "Account",;
     PRETRAN Char(2) DESCRIPTION "Pretran",;
     AFSREP Char(14) DESCRIPTION "Afsrep",;
     REPKEY Char(9) DESCRIPTION "Repkey",;
     BRANCH Char(3) DESCRIPTION "Branch",;
     WODEALER Char(5) DESCRIPTION "Wodealer",;
     BANKCODE Char(2) DESCRIPTION "Bankcode",;
     COMMRATE Decimal(6,4) DESCRIPTION "Commrate",;
     NEWREP Char(1) DESCRIPTION "Newrep",;
     SETTLE Char(1) DESCRIPTION "Settle",;
     POSTDATE Char(6) DESCRIPTION "Postdate")
if file("cisamdemo.str")
    return .T.
else
    return .F.
endif
// end of createtab.prg

Server-side 4GL programs can be called by all clients, e.g. from a Java class with a JDBC connection:

//---------------------------------
//-- create_str.java --
//---------------------------------
import java.sql.*;
import java.io.*;
import Recital.sql.*;

public class create_str {

  public static void main(String argv[]) {
    try {
      new RecitalDriver();
      String url = "jdbc:Recital:" +
        "SERVERNAME=cisamserver;" +
        "DIRECTORY=/usr/recital/data/southwind;" +
        "USERNAME=user;" +
        "PASSWORD=password";
      Connection con = DriverManager.getConnection(url, "user", "pass");
      Statement stmt = con.createStatement();

      CallableStatement sp = con.prepareCall("{call createtab}");
      boolean res = sp.execute();
      String outParam = sp.getString(1);
      System.out.println("Returned "+outParam);
      sp.close();
      con.close();
    } catch (Exception e) {
      System.out.flush();
      System.err.flush();
      DriverManager.println("Driver exception: " + e.getMessage());
      e.printStackTrace();
    }
    try {
      System.out.println("Press any key to continue...");
      System.in.read();
    } catch(IOException ie) {
      ;
    }
  }
}

The table should be given a ‘.str’ file extension (rather than the default ‘.dbf’) to signify that this is a structure file only.

Please see the end of this article for information on matching Informix and Recital data types

Fig 4: Recital CREATE/MODIFY STRUCTURE worksurface for character mode table creation.

Step 2: Creating the Bridge File

If you have Recital installed on the server platform, the Bridge File can be created using the CREATE BRIDGE worksurface.  The corresponding command to modify the bridge file is MODIFY BRIDGE <bridge file>.  This is the cisamdemo.dbf bridge file in the CREATE/MODIFY BRIDGE WORKSURFACE:

> modify bridge cisamdemo.dbf

Fig 5: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface for bridge creation.

For Recital Database Server clients, the Bridge File can be created using the Recital/SQL CREATE BRIDGE command:

Recital/SQL CREATE BRIDGE:

CREATE BRIDGE cisamdemo.dbf;
  TYPE "CISAM";
  EXTERNAL "cisamdemo.dat";
  METADATA "cisamdemo.str";
  ALIAS "cisamdemo"

or:

CREATE BRIDGE cisamdemo.dbf;
  AS "type=CISAM;external=cisamdemo.dat;metadata=cisamdemo.str;alias=cisamdemo"

The examples above assume that the C-ISAM file, the bridge file and the Recital structure file are all in the current working directory.  Full path information can be specified for the <externalname> and the <databasename>.  For added flexibility, environment variables can be used to determine the path at the time the bridge is opened.  Environment variables can be included for either or both the <externalname> and the <databasename>.  A colon should be specified between the environment variable and the file name.

e.g.

  CREATE BRIDGE cisamdemo.dbf;
  TYPE "CISAM";
  EXTERNAL "DB_DATADIR:cisamdemo";
  METADATA "DB_MIRAGE_PATH:cisamdemo.str";
  ALIAS "cisamdemo"

Recital CREATE BRIDGE/MODIFY BRIDGE worksurface:

Fig 6: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface - using environment variables.

Using the Bridge

The Bridge can now be used.  To access the C-ISAM file, use the ‘alias’ specified in the Bridge definition.

SQL:

SELECT * FROM cisamdemo

Recital/4GL:

use cisamdemo

Indexes

The cisamdemo.dat file included in the Recital distributions for Linux and UNIX has three associated index keys in the cisamdemo.idx file:

Select area: 1
Database in use: cisamdemo
Alias: cisamdemo
Number of records: 4
Current record: 2
File Type: CISAM (C-ISAM)
Master Index: [cisamdemo.idx key #1]
Key: DD+CONFIRM+PROCDATE+CONTROL
Type: Character
Len: 21   (Unique)
Index: [cisamdemo.idx key #2]
Key: DD+SUBSTR(CONFIRM,2,5)+TRADDATE+STR(DOLLARS,13,2)
     +CURRTRAN+ACCOUNT
Type: Character
Len: 42
Index: [cisamdemo.idx key #3]
Key: DEALER+BRANCH+AFSREP+SUBSTR(PROCDATE,5,2)
     +SUBSTR(CONTROL,2,4)
Type: Character
Len: 28

The Recital C-ISAM bridge makes full use of the C-ISAM indexes.  SQL SELECT statements with WHERE clauses are optimized based on any of the existing indexes when possible.  The following ODBC SELECT call makes use of key #3 rather than sequentially searching through the data file.

SQLExecDirect:
  In:      hstmt = 0x00761BE8,
    szSqlStr = "select * from cisamdemo
      where dealer+branch+afsrep=' 00161   595-7912",
      cbSqlStr = -3
  Return:  SQL_SUCCESS=0

Get Data All:

"DD", "CONFIRM", "PROCDATE", "CONTROL", "DOLLARS", "DEALER", 
"TERRITORY", "WOREP", "CURRTRAN", "TRADDATE", "CITY", "ACCOUNT", 
"PRETRAN", "AFSREP", "REPKEY", "BRANCH", "WODEALER", "BANKCODE", 
"COMMRATE", "NEWREP", "SETTLE", "POSTDATE"

"0159", " 15522", "930312", "13356", 4992.60, "00161", "19", 
"", "210", "930305", "", "70000100009", "", "595-7912", 
"930315791", "", "", "59", 0.0000, "1", "", "930315"
1 row fetched from 22 columns.

Using the Recital/4GL, the primary index is set as the master index when the bridge is first opened.  Any secondary indexes can be selected using the SET ORDER TO <expN> command.  The Recital/4GL SEEK or FIND commands and SEEK() function can be used to search in the current master index.

> SET ORDER TO 3
Master index: [cisamdemo.idx key #3]
> SEEK “00161   595-7912”

Appendix 1: Data Types

Appendix 2: C-ISAM RDD Error Messages

The following errors relate to the use of the Recital CISAM Replaceable Database Driver (RDD).  They can be received as an ‘errno <expN>’ on Recital error messages:

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Graphical Installation

Note: The installation must be run as root. For systems with a hidden root account, please use ’Run as Root’.

1. Download the distribution file into a temporary directory
2. Check that the distribution file has the execute permission set
3. Run the distribution file
4. Follow the on screen instructions:
   1. License agreement
   2. Select components
   3. Installation directory and shortcuts
   4. Linking to /usr/bin
   5. ODBC Installation type (Recital Server / Recital Client Drivers)
   6. Java Virtual Machine selection (Recital Server / Recital Client Drivers)
   7. TomCat Installation type (Recital Server / Recital Client Drivers)
   8. Apache Firecat Plugin Installation (Recital Web Developer)
   9. Replication Service Type (Recital Replication Server)
   10. Install license file

Text Installation

Note: The installation must be run as root. For systems with a hidden root account, please precede commands with ’sudo’.

1. Download the distribution file into a temporary directory
2. Check that the distribution file has the execute permission set
3. Run the distribution file
4. Follow the on screen instructions:
   1. License agreement
   2. Select components
   3. Installation directory and shortcuts
   4. Linking to /usr/bin
   5. ODBC Installation type (Recital Server / Recital Client Drivers)
   6. Java Virtual Machine selection (Recital Server / Recital Client Drivers)
   7. TomCat Installation type (Recital Server / Recital Client Drivers)
   8. Apache Firecat Plugin Installation (Recital Web Developer)
   9. Replication Service Type (Recital Replication Server)
   10. Install license file

When you start the loadbalancer.org appliance you will see the following:

Default login:
Username: root
Password: loadbalancer

Access to webclient from an external client is:
http://192.168.1.129:9080
http://192.168.1.129:9443

You can access the web administrator using the IP and ports described onscreen.

For the sri lanka porject we are looking for performance and the network diagram indicates we are happy to have the cluster on the same subnet as the rest of the network.

Direct routing is the fasted performance possible, it has the advantage over NAT that the Loadbalancer does not become a bottleneck for incoming and outgoing packets. With DR the loadbalancer simply examines incoming packets and the servers to route the packets directly back to the requesting user.

The web interfaceis the only way to fully configure the loadbalancer vm. The console tool lbwizard will get it initiallised and any further configurations can then be done via the webinterface.

Using lbwizard for the Sri lanka configuration follow these steps.

On the first Loadbalancer:

//Start

Is this unit part for a HA Pair?
YES

Have you already setup the Slave?
NO

Is this a one-armed configuration?
YES

Enter the IP Address for the interface eth0?
Enter IP address you wish to be assigned to the SLAVE loadbalancer.

Enter the netmask for interface eth0?
Enter netmask for the subnet.

Enter the Floating IP adrress?
Enter the IP address that will be IP assosiacted the the HA-pair of loadbalancers.

//Finish

On the 2nd loadbalancer VM, run the lbwizard.

//Start

Is this unit part of an HA-Pair?
YES

Have you already set up the Slave?
YES

What is the slave units UP address?
Enter the IP which you entered when configuring the other loadbalancer VM.

Is this a one-armed configuration?
YES

Enter the IP Address for the interface eth0?
Enter the IP that will be assigned to the MASTER loadbalancer

Enter the netmask for interface eth0?
Enter the subnet netmask.

Enter the Floating IP address?
Enter the IP address that will be IP assosiacted the the HA-pair of loadbalancers.

Enter the address of the default gateway?
Enter the deafult gateway for the subnet.

Enter the IP of the nameserver?
Enter the dns server.

Enter the port for the first Virtual server?
Enter 22 for ssh

Enter the IP address of the first real server?
Enter the real IP of the first appserver

//Finish

Now this is complete we need to go to the web admin interface to configure the 2nd Real Server. As the lbwizard program will only allow you to configure 1 real server.

Now login to the web admin using the default password:

username: loadbalancer
password: loadbalancer

Note: Connect to the IP you have now set for your master loadbalancer

Goto the edit configuration tab

Now click add a real server:

Enter a label
IP address of the server plus the port of the service i.e. 192.168.1.125:22


Edit Configuration -> Virtual Servers

persistancte -> NO

Scheduler-> LC
LC - Least-Connection: assign more jobs to real servers with
fewer active jobs.

Service to check -> custom1

Check port -> 22

Forwarding Method -> DR

Feedback Method -> Agent

Arp Problem when using DR

Every real server must be configured to respond to the VIP address as well as the RIP
address.

You can use iptables (netfilter) on the real server to re-direct incoming packets destined for the virtual
server IP address.

This is a simple case of adding the following command to your start up script (rc.local):

//replace 10.0.0.21 with the Virtual Server IP
iptables -t nat -A PREROUTING -p tcp -d 10.0.0.21 -j REDIRECT

chkconfig iptables on