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

Click image to display full size

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

Click image to display full size

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

Click image to display full size

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:

After split brain has been detected, one node will always have the resource in a StandAlone connection state. The other might either also be in the StandAlone state (if both nodes detected the split brain simultaneously), or in WFConnection (if the peer tore down the connection before the other node had a chance to detect split brain).

At this point, unless you configured DRBD to automatically recover from split brain, you must manually intervene by selecting one node whose modifications will be discarded (this node is referred to as the split brain victim). This intervention is made with the following commands:

# drbdadm secondary resource 
# drbdadm disconnect resource
# drbdadm -- --discard-my-data connect resource

On the other node (the split brain survivor), if its connection state is also StandAlone, you would enter:

# drbdadm connect resource

You may omit this step if the node is already in the WFConnection state; it will then reconnect automatically.

If all else fails and the machines are still in a split-brain condition then on the secondary (backup) machine issue:

drbdadm invalidate resource

Recital is a dynamic programming language with an integrated high performance database particularly well suited for the development and deployment of high transaction throughput applications.  Recital 10 further enhances Recital with extensive features and functionality to facilitate its use in fault tolerant high availability systems. Much of the development of Recital 10 was concentrated on performance optimizations and cluster aware functionality to provide an application platform that can be scaled as needed without any application changes. 

Key features of Recital 10 include:

• Cluster aware database engine that works transparently with drbd, heartbeat, glusterfs and samba
• High degree of fault tolerance with self healing indexes
• Massive performance improvements 
• Extensive internals overall and modernization with superior object-oriented capabilities
• Chronological data versioning with database timelines
• SmartQuery caching
• Database Administration Tools
• Code and Data Profiling
• Better integration with unix/linux command shell
• Incorporates a range of new built-in functions compatible with those in the PHP core libraries
• Built-in support for outputting data in HTML, XML, and JSON format
• Seamless SQL command integration into the Recital scripting language
• Much improved Microsoft FoxPRO language compatibility
• Numerous extensions and improvements (see below for details)
• Very large file support (2^63)