Recital

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Another useful article on IBM developerworks shows how to build PHP extensions using SWIG. You can find the article here.
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We are pleased to announce the release of Recital 10.0.2.

Here is a brief list of features and functionality that you will find in the 10.0.2 release. 

  • New commands
    SAVE/RESTORE DATASESSION [TO variable]
    CONNECT "connectString"
    DISCONNECT 
  • New functions (OData compatible)
    startsWith(haystack as character, needle as character)
    endsWith(haystack as character, needle as character)
    indexOf(haystack as character, needle as character)
    substringOf(haystack as character, needle as character)
    concat(expC1, expC2)
  • New system variables
    _LASTINSERTEDSYNCNUM
  • Enhanced commands
    Added CONNSTRING "connectingString" to the USE command to connect to remote servers (Recital, MySQL, PostgreSQL, Oracle, ODBC)
  • Further SQL query optimizer improvements to boost performance
  • Performance improvements in Recital Web
  • Forced all temporary files into temp directory (improves performance when local tmpfs is used as temp directory and reduces network i/o)
  • Fixed cookie and session variable problems in Recital Web
  • Fixed problem with temporary files being left after some server queries involving memos and object data types
  • Improved performance of the Windows ODBC driver
  • Fixed a security flaw in Recital Web
  • Fixed all reported bugs 
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Subclipse is an Eclipse Team Provider plug-in providing support for Subversion within the Eclipse IDE. This plugin is required in order to use the recital eclipse workspace.
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In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to work with Triggers in the Recital Database Server.

Overview

A trigger is a special kind of stored procedure that runs when you modify data in a specified table using one or more of the data modification operations: UPDATE, INSERT, or DELETE.

Triggers can query other tables and can include complex SQL statements. They are primarily useful for enforcing complex business rules or requirements. For example, you can control whether to allow a new order to be inserted based on a customer's current account status.

Triggers are also useful for enforcing referential and data integrity.

Triggers can be used with any data source that is handled natively by the Recital Database Engine. This includes Recital, FoxPro, FoxBASE, Clipper, dBase, CISAM, and RMS data,

Creating and Editing Triggers

To create a new Trigger,  right-click the Procedures node in the Databases tree of the Project Explorer and choose Create. To modify an existing Trigger select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it, or select Modify from the context menu. By convertion we recommend that you name your Stored Procedures beginning with "sp_xxx_", user-defined functions with "f_xxx_", and Triggers with "dt_xxx_", where xxx is the name of the table that they are associated with.

Associating Triggers with a Table

Once you have written your Triggers as detailed above you can associate them with the operations performed on a Table by selecting the Table tab.

The Tables tab allows you to select a Trigger procedure by clicking on the small button at the right of the Text field.

Types of Triggers

As can be seen from the Tables tab detailed below, The Recital Database Server handles 6 distinct types of Triggers.

Open Trigger

The Open Trigger is called after is a table is opened but before any operations are performed on it. You can use this trigger to record a log of table usage or provide a programmable means of checing security. If the Trigger procedure returns .F. (false), then the table is not opened. You can use a TRY...CATCH block around the associated command to inform the user.

Close Trigger

The Close Trigger is called just prior to a table being closed. In this trigger you may find it useful to get transaction counts by using the IOSTATS() built-in 4GL function, and record these values in a transaction log.

Update Trigger

The Update Trigger is called prior to a record update operation being performed. You can use this trigger to perform complex application or data specific validation. If the Trigger procedure returns .F. (false), then the record is not updated. You can use inform the user from within the Trigger procedure the reason that the data cannot be updated.

Delete Trigger

The Delete Trigger is called prior to a record delete operation being performed. You can use this trigger to perform complex application or data specific validation such as cross-table lookups e.g. attempting to delete a customer recortd when there are still open orders for that specific customer. If the Trigger procedure returns .F. (false), then the record is not deleted.

Insert Trigger

The Insert Trigger is called prior to a record insert (append) operation being performed. You can use this trigger to perform such tasks as setting up default values of columns within the record. If the Trigger procedure returns .F. (false), then the record is not inserted.

Rollback Trigger

The RollbackTrigger is called prior to a rollback operation being performed from within a form. If the Trigger procedure returns .F. (false), then the record is not rolled back to its original state.

Testing the Trigger

To test run the Trigger, select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it. Once the Database Administrator is displayed, click the Run button to run the Trigger.

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This article examines the advantages of using databases and looks at how to create databases for new and existing applications.

Overview

file which contains information, including full path details, about all the files that belong to that particular database. Opening a database gives an application access to all that database's files - operating system and data dictionary protection and security permitting - in whichever directory on the system they reside and database commands can target the files as a single unit.

NOTE: The word 'database' has often been used in Xbase products to refer to an individual '.dbf' file. In this article these are referred to as 'tables' and a database may contain many tables.

Advantages

Recital has always offered developers the maximum in flexibility in the design and deployment of their applications. The SET DEFAULT and SET PATH commands along with the ability to access files via their full Operating System path name has allowed data and code to be created and stored in any required location. Such flexibility does however put the onus on the developer to manage all elements of the application and ensure that maintenance tasks cover all files. The introduction of the database commands retains the established developer-driven design, but provides functionality to facilitate the access and maintenance of the components of that design. The functionality offered is in three main areas:

  • Facilitate data access
  • Facilitate the storage and extraction of information about the files in an application
  • Facilitate the maintenance of the files in an application

These three areas are looked at in more detail in the sections below.

Data Access

The immediate effect of using a database is that all the database's tables and associated files (indexes, dictionaries, memo files) are accessible with the issue of a single command, the OPEN DATABASE command.
// Open the database
> open database southwind
// List the database tables
> list tables
Tables in Database southwind:
Name Source
categories /usr/recital/data/southwind/categories.dbf
customers /usr/recital/data/southwind/customers.dbf
employees /usr/recital/data/southwind/employees.dbf
example /usr/recital/data/southwind/example.dbf
order_details /usr/recital/data/southwind/order_details.dbf
orders /usr/recital/data/southwind/orders.dbf
productsbyname /usr/recital/data/southwind/productsbyname.dbf
products /usr/recital/data/southwind/products.dbf
shippers /usr/recital/data/southwind/shippers.dbf
suppliers /usr/recital/data/southwind/suppliers.dbf
cisamdemo /usr/recital/data/southwind/cisamdemo.dbf
> use example
In the case of the sample southwind database that ships with Recital products on all platforms and is shown above, this effect can be achieved in other ways (SET PATH or SET DEFAULT), since its files all reside in the southwind directory. The database advantage comes when the database catalog contains files from multiple directories, e.g.
// Open the database
> open database myapp
// List the database tables
> list tables
Tables in Database myapp:
Name Source
zipcodes /usr/myapp/data/lookups/zipcodes.dbf
customers /usr/myapp/data/current/customers.dbf
archive03 /usr/myapp/data/archive/archive03.dbf
archive04 /usr/myapp/data/archive/archive04.dbf
users /usr/allapps/data/users.dbf
menus /usr/myapp/data/system/menus.dbf
// Open a table
> use users
The OPEN DATABASE command requires only the database name to be specified, not the complete path of a directory as with SET PATH or SET DEFAULT. Databases are searched for in the sub-directories of the directory defined in the DB_DATADIR environment variable or symbol. DB_DATADIR is set in the system wide configuration file.
#---------------------------------------------------
# location of directories and important files
#---------------------------------------------------
DB_DATADIR="${ROI_ROOT}data/" ;export DB_DATADIR
NOTE: DB_DATADIR is read from these files at startup to determine the home directory for databases. Updates to DB_DATADIR once a Recital process is running do not change this setting. The OPEN DATABASE command and certain other database commands allow a '?' to be specified in place of a database name. In this case the 'Select a file' dialog is displayed, listing the available files in the DB_DATADIR directory.

Click image to display full size

Fig 1: Recital Terminal Developer OPEN DATABASE ? command.

This functionality is also supported by the PACK DATABASE, REBUILD DATABASE and REINDEX DATABASE commands.

Databases can also simplify data access for Recital Client Drivers using the Recital Database Server: instead of specifying a starting directory, only a database name is required. The database can handle files from multiple directories and associate tables with their single index files.
Recital Universal .NET Data Provider
/////////////////////////////////////////
// include the references below
using System.Data;
using Recital.Data;

/////////////////////////////////////////
// sample code to call a Stored Procedure
public int CallStoredProcedure()
{
string source = "Data Source=localhost;" +
"Database=southwind;" +
"uid=?;"+
"pwd=?";

RecitalConnection conn = new RecitalConnection(source);
...
Recital Universal JDBC Driver
import java.sql.*;
import java.io.*;
import java.net.URL;
import java.math.BigDecimal;
import Recital.sql.*;

public class jdbc_test {

public static void main(String argv[]) {
int i;
ResultSet rs;
ResultSetMetaData rsmd;

System.out.println("Recital JDBC driver verification.");

for (int ii=0; ii<1; ++ii) {
try {
//----------------------------------------------------------
//-- Load the Client Driver for the
//-- Recital Universal Application Server
//----------------------------------------------------------
System.out.println("Loading Recital JDBC driver.");
new RecitalDriver();
//-----------------------------------------------------------
//-- The standard format of the connection URL is as follows:
//-----------------------------------------------------------
String url = "jdbc:Recital:" +
"SERVERNAME=?;" +
"DATABASE=jdbc_test;" +
"USERNAME=?;" +
"PASSWORD=?;" +
"ENCRYPTION=false";
...
Windows Recital Universal ODBC Driver

Click image to display full size

Fig 2: Recital Universal ODBC Driver DSN setup using a database.
Database Procedure Libraries
A database can have an associated procedure library, which is automatically opened when the database is opened. This way, any procedures required by the database's data files are always available. The procedure library should reside in the database's directory and be named dbc_xxx_library.prg, where 'xxx' is the name of the database. When the OPEN DATABASE command is issued, a check is made for the database procedure library and a SET PROCEDURE TO dbc_xxx_library.prg ADDITIVE issued automatically. The procedure library is in turn closed when the CLOSE DATABASES command is issued. This is particularly convenient for client/server database access.
Database Events
Issuing the OPEN DATABASE or CLOSE DATABASES command also fires a database event. Database events, like triggers for tables and forms, can have programs associated with them. The OPEN DATABASE command fires the DBC_OPENDATA event and will run a program called db_opendata.prg if one exists in the database's directory. Similarly, the CLOSE DATABASES command fires the DBC_CLOSEDATA event and runs the db_closedata.prg program. Both of these events also allow the current open or close operation to be abandoned if the associated program returns a logical false (.F.).

Information

Databases, specifically database catalogs, are an excellent place to store information about the files required by a particular application. Instead of having to search through application code to determine which tables are being used and what index keys they have, this information can be viewed in the database catalog. Database catalogs are themselves Recital tables and can be viewed and/or updated in the same way as any other Recital table. There is also a series of commands to provide information about the currently open database. DISPLAY/LIST DATABASE The DISPLAY DATABASE and LIST DATABASE commands display the database name and path, followed by the equivalent of LIST STRUCTURE INDEX and LIST DICTIONARY for each table in the database, e.g.
> open database southwind
> display database
Database Name:  southwind
Database Path: /usr/recital-9.0/data/southwind/

Structure for database : categories.dbf
Number of data records : 8
Date of creation : 05/12/2004
Date of last update : 05/12/2004
Database encrypted : False

Field Field Name Type Width Dec Description 1 CATEGORYID Numeric 10 Category ID 2 CATEGORYNAME Character 15 Category Name 3 DESCRIPTION Memo 8 Description 4 PICTURE Memo 8 Picture ** Total ** 42
Production DBX file: categories.dbx
Master Index TAG: CATEGORYID
Key: categoryid
Type: Binary
Len: 8
...
DISPLAY DATABASE shows the data one screen at a time, whereas LIST DATABASE is ideal for output to a file.
> open database southwind
> list database to file info.txt
DISPLAY/LIST TABLES
LIST TABLES, as we have seen above, lists all the tables from the database, giving each table's name and path. DISPLAY TABLES shows the information one screen at a time.

Maintenance

Using a database can simplify the maintenance of an application's programs, tables and indexes. Multiple files, possibly in different directories, can be targeted by a single database command.
COMPILE DATABASE
The COMPILE DATABASE command can be used to issue a COMPILE command for all program files listed in the database catalog.
// Open the database
open database myapp

// Compile all the database's programs
compile database
NOTE: Program files are added to a database using the SQL CREATE PROCEDURE command.
PACK DATABASE
The PACK DATABASE command issues a PACK command for every table in the database catalog. The PACK command is used to permanently remove any records that have been marked for deletion using the DELETE command.
// Open the database
open database southwind
// Pack all the database's tables
pack database
REINDEX DATABASE
The REINDEX DATABASE command rebuilds all the tag and single indexes in the catalog. This is the equivalent of an INDEX ON <key> TO | TAG <index> for each catalogued index key.
// Open the database
open database southwind
// Rebuild all the database's indexes
reindex database
NOTE: Using a database helps protect against a table being opened without its associated single index files also being opened. Any single index files that are included in the database catalog will automatically be opened when their table is opened via the database. If a single index appears in the database catalog, but the physical file no longer exists, it will be removed from the catalog when its associated table is next opened. All indexes, tagged indexes or single indexes, created while the database is open, are added automatically to the database catalog.
REBUILD DATABASE
The REBUILD DATABASE command is used to PACK, rebuild the index tags and refresh the contents of the database catalog file.
// Rebuild the database
rebuild database southwind

Creating and populating a database

Databases are created using the CREATE DATABASE command.
// Create new database
create database newdb
The CREATE DATABASE creates a sub-directory in the DB_DATADIR and initializes the new database's catalog file. The catalog file is given the same basename as the database and is a Recital table with a '.cat' file extension. It has a production index file with a '.cax' file extension and a memo file with a '.cam' file extension.
// Open the database
open database newdb
With the database open, the catalog file table is opened in the highest available workarea and is given an alias name of its basename preceded by an underscore, e.g. '_newdb'. Any new tables or indexes that are created will be automatically added into the catalog and form part of the database. 'Free' tables can also be manually added into a database using the SQL ADD TABLE command.
// config.db
set sql on
set sql to vfp
// end of config.db

// Create a 'free' table, with no database open
create table free1 (field1 char(10), field2 date)
// Open the database
open database newdb
add table free1
As the application runs, 'myapp' in the example above, each table that is opened is added to the database catalog. Indexes that are opened are added in the same way. Using SET AUTOCATALOG OFF, inclusion in the catalog can be restricted. Once all required areas of the application have been catalogued, the application can be updated to make use of the database commands.

Converting an existing application

The AUTOCATALOG commands can be used to automatically create a database catalog based on an existing application. The SET AUTOCATALOG TO >database< command will create the database if it does not already exist.
// Database must be closed during autocatalog process
close databases
// Specify the database
set autocatalog to myappdb
// Start the autocatalog process
set autocatalog on
do myapp
// The autocatalog process can be toggled off to exclude
// certain parts of the application if required
// set autocatalog off

Exporting a database

The BACKUP DATABASE and RESTORE DATABASE commands have been added to simplify the process of moving applications between binary incompatible platforms. Binary files such as tables, memo files and data dictionaries must be exported to ASCII format to allow them to be transferred from one platform to another where the platforms have different binary ordering. For example, this is the case when moving files between a SUN Sparc Solaris machine and an Intel Linux machine. The BACKUP DATABASE and RESTORE DATABASE commands are extensions of the BUILD and INSTALL commands: where BUILD and INSTALL operate on a specified list of tables, BACKUP DATABASE and RESTORE DATABASE automatically handle an entire database.
// Open the database
open database southwind
// Export the database to ASCII format
backup database
The BACKUP DATABASE command goes through the database catalog, exporting each file into an ASCII format that can be handled by the RESTORE DATABASE command. The files are created in a directory with the same name as the database. This directory is a sub-directory of the directory specified in the environment variable DB_BACKUPDIR and is created automatically. By default, DB_BACKUPDIR is the 'backup' sub-directory of the Recital home directory.
// Query the DB_BACKUPDIR environment variable setting
> ? getenv([DB_BACKUPDIR])
/usr/recital/backup
Like DB_DATADIR, DB_BACKUPDIR is set in the system-wide configuration file and is read at startup to determine the home directory for database backups. Updates to DB_BACKUPDIR once a Recital process is running do not change this setting.
# profile.db/uas extract
#---------------------------------------------------
# location of directories and important files
#---------------------------------------------------
DB_BACKUPDIR="${ROI_ROOT}backup/" ;export DB_BACKUPDIR
Once the BACKUP DATABASE command has completed, the files can be transferred to another platform, for example from Intel SCO OpenServer to IBM AIX and the RESTORE DATABASE command used to recreate the database.
// Export the database to ASCII format
// Note: the BACKUP DATABASE command operates
// on the active or specified database
$ db
> backup database southwind
> quit

// 'tar' up the files for transfer
$ cd /usr/recital/backup
$ tar cvf southwind.tar ./southwind

// Transfer the tar archive to DB_BAKUPDIR on the
// target machine, then extract the files
$ pwd
/usr/recital/backup
$ tar xvf southwind.tar

// Rebuild the database on the target platform
// The database is automatically created
// as a sub-directory of DB_DATADIR
$ db
> restore database southwind
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In this article Barry Mavin, CEO and Chief Software Architect for Recital provides details on how the Recital Database Server can be used to provide a solution for Universal Data Integration.

Overview

The Recital Database Server handles universal cross-platform data access to a wide range of data sources. The database server natively handles full remote SQL data access to Recital, Visual FoxPro, FoxPro, FoxBASE, Clipper and older dBase data. Using Bridges, it handles full remote SQL data access to C-ISAM and OpenVMS RMS. Using gateway connections, it handles full remote SQL data access to Oracle, MySQL, PostgreSQL, SQL Server, server-side ODBC, server-side JDBC and server-side OLE DB data sources. With its ability to access data using server-side ODBC, JDBC and OLE DB drivers from clients on all supported operating systems (Windows, Linux, Unix, OpenVMS), the Recital Database Server is an ideal Data Integration Solution for applications of all sizes and complexity.

Universal Data Integration Solutions

There are several ways in which data may be accessed by the Database Server.

Table 1:

Client Universal Data Access solutions for accessing local or remote data.


Client Solution
Recital Use remote gateway connections
Visual FoxPro Use the Universal ODBC Driver
Java (all platforms) Use the Universal JDBC Driver
.NET Framework Use the Universal .NET Data Provider
Microsoft Office Use the Universal ODBC Driver
Windows Mobile Use the Universal Compact Framework .NET Data Provider
PHP on Linux Use the Universal ODBC Driver for Linux
Mono on Linux Use the Universal .NET Data Provider
Others If the data source you want to access is not in the list above, then you can use a remote ODBC, JDBC or OLE DB gateway.
You can find examples of connection strings for most ODBC and OLE DB data sources by clicking here.

Table 2:

Windows Server Universal Data Access solutions accessible from any remote client running on Windows, Linux, Unix or OpenVMS:


Data Source Solution
Recital Native support (See table 1)
Visual FoxPro Native support (See table 1)
FoxPro Native support (See table 1)
FoxBASE Native support (See table 1)
Clipper Native support (See table 1)
dBase Native support (See table 1)
C-ISAM Use a bridge (See table 1)
Access Use a gateway connection
gateway="oledb:Provider=Microsoft.Jet.OLEDB.4.0;Data Source=\somepath\mydb.mdb;User Id=admin;Password=;"
Exchange Use a gateway connection
gateway="oledb:Provider=ExOLEDB.DataSource;Data Source=http://servername/publicstore"
Excel Use a gateway connection
gateway="oledb:Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyExcel.xls;"
Oracle Use a gateway connection
gateway="oledb:Provider=msdaora;Data Source=TheOracleDB;User Id=xxxxx;Password=xxxxx;"
SQL Server Use a gateway connection
gateway="oledb:Provider=sqloledb;Data Source=Aron1;Initial Catalog=pubs;User Id=sa;Password=asdasd;"
MySQL Use a gateway connection
gateway="oledb:Provider=MySQLProv;Data Source=mydb;User Id=xxxxx;Password=xxxxx;"
IBM DB2 Use a gateway connection
gateway="oledb:Provider=DB2OLEDB;Network Transport Library=TCPIP;Network Address=XXX.XXX.XXX.XXX;Initial Catalog=MyCtlg;Package Collection=MyPkgCol;Default Schema=Schema;User ID=MyUser;Password=MyPW"
Sybase ASA Use a gateway connection
gateway="oledb:Provider=ASAProv;Data source=myASA"
Sybase ASE Use a gateway connection
gateway="oledb:Provider=Sybase.ASEOLEDBProvider;Srvr=myASEserver,5000;Catalog=myDBname;User Id=username;Password=password"
IBM Informix Use a gateway connection
gateway="oledb:Provider=Ifxoledbc.2;password=myPw;User ID=myUser;Data Source=dbName@serverName;Persist Security Info=true"
Ingres Use a gateway connection
gateway="odbc:dsn=data_source_name"
Firebird Use a gateway connection
gateway="odbc:dsn=data_source_name"
IBM AS400 iSeries Use a gateway connection
gateway="oledb:PROVIDER=IBMDA400; DATA SOURCE=MY_SYSTEM_NAME;USER ID=myUserName;PASSWORD=myPwd"
Interbase Use a gateway connection
gateway="oledb:provider=sibprovider;location=localhost:;data source=c:\databases\gdbs\mygdb.gdb;user id=xxxxx;password=xxxxx"
Others

If the data source you want to access is not in the list above, then you can use server-side ODBC, JDBC or OLE DB.
You can find examples of connection strings for most ODBC and OLE DB data sources by clicking here.
Full details on using server-side JDBC drivers can be found here.
Full details on using server-side ODBC drivers can be found here.
Full details on using server-side OLE DB drivers can be found here.


Table 3:

Linux and Unix Server Universal Data Access solutions accessible from any remote client running on Windows, Linux, Unix or OpenVMS:


Data Source Solution
Recital Native support (See table 1)
Visual FoxPro Native support (See table 1)
FoxPro Native support (See table 1)
FoxBASE Native support (See table 1)
Clipper Native support (See table 1)
dBase Native support (See table 1)
C-ISAM Use a bridge (See table 1)
Oracle Use a gateway connection
gateway="oracle:Connection_String"
MySQL Use a gateway connection
gateway="mysql:Connection_String"
IBM DB2 Use a gateway connection
gateway="db2:Connection_String"
PostgreSQL Use a gateway connection
gateway="postgres:Connection_String"
Others

If the data source you want to access is not in the list above, then you can use a server-side JDBC driver.
Full details on using server-side JDBC drivers can be found here.


Table 4:

OpenVMS Server Universal Data Access solutions accessible from any remote client running on Windows, Linux, Unix or OpenVMS:


Data Source Solution
Recital Native support (See table 1)
Visual FoxPro Native support (See table 1)
FoxPro Native support (See table 1)
FoxBASE Native support (See table 1)
Clipper Native support (See table 1)
dBase Native support (See table 1)
RMS Use a bridge (See table 1)
Others

If the data source you want to access is not in the list above, then you can use a server-side JDBC driver.

Supported Data Sources

Native Data Access

The Recital Database Server has native built-in support for the following data sources:

  • Recital
  • Visual FoxPro
  • FoxPro
  • FoxBASE
  • Clipper
  • dBase

You can setup tables to work with using the Database Administration Tool in Recital Enterprise Studio.

Bridges

Using Bridges, you can access the following data sources as if they were standard Recital/FoxPro tables:

  • CISAM
  • OpenVMS RMS

You can setup bridges using the Database Administration Tool in Recital Enterprise Studio.

Gateways/Connections

Using Gateways, you can transparently access the following local or remote data sources:

  • Recital
  • Oracle
  • ODBC (Server-side ODBC data sources)
  • JDBC (Server-side JDBC data sources)
  • OLEDB Use this to connect to SQL Server and other Windows OLE DB data sources)
  • MySQL
  • PostgreSQL

Remote Data Object functions

Recital 10 includes a complete and robust set of data source independent functions for accession MySQL, Oracle, DB2 and Postgres. This article explains how to use them.

Client Data Access drivers

Included with the Recital Database Server are three Client drivers. These Client drivers can access any data sources supported by the Recital Database Server. They are not restricted to accessing only Recital data. They can be used to access server-side ODBC, JDBC and OLE DB data sources also.

Recital Universal .NET Data Provider

Use this client driver when building .NET applications with Visual Studio .NET. A data provider in the .NET Framework serves as a bridge between an application and a data source. A data provider is used to retrieve data from a data source and to reconcile changes to that data back to the data source.

Key features of the Recital Universal .NET Data Provider:

  • Fully Internet enabled
    The Recital Universal .NET Data Provider works across the internet providing access to a wide range of data sources located on remote servers running Windows, Linux, Unix and OpenVMS.
  • SQL Server compatible
    The Recital Universal .NET Data Provider is plug compatible with the .NET Framework SQL Server Data Provider.
  • Cross-platform Data Integration
    Using the Recital Universal .NET Data Provider, you can connect to remote Windows, Linux, Unix or OpenVMS servers and access any data source supported by the Recital Database Server.
  • Managed code
    The Recital Universal .NET Data Adaptor written in C# is 100% .NET Framework managed code.
  • Runs on Windows Mobile
    The Recital Universal .NET Data Adaptor runs under the .NET Compact Framework on Windows Mobile.
Recital Universal JDBC Driver

The JDBC API is the industry standard for database-independent connectivity between the Java programming language and a wide range of databases. The JDBC API provides a call-level API for SQL-based database access. JDBC technology allows you to use the Java programming language to exploit "Write Once, Run Anywhere" capabilities for applications that require access to enterprise data.

Key features of the Recital Universal JDBC Driver:

  • Fully Internet enabled
    The Recital Universal JDBC driver works across the internet providing access to a wide range of data sources located on remote servers running Windows, Linux, Unix and OpenVMS.
  • JDBC 3.0 API
    The Recital Universal JDBC driver supports the JDBC 3.0 API.
  • Pure Java Type 3 Driver
    The Recital Universal JDBC driver is a 100% pure Java Type 3 driver.
  • Full Access to Metadata
    The JDBC API provides metadata access that enables the development of sophisticated applications that need to understand the underlying facilities and capabilities of a specific database connection.
  • Cross-platform Data Integration
    Using the Recital Universal JDBC driver, you can connect to remote Windows, Linux, Unix or OpenVMS servers and access any data source supported by the Recital Database Server.
  • No Installation
    A pure JDBC technology-based driver does not require special installation; it is automatically downloaded as part of the applet that makes the JDBC calls. The Recital Universal JDBC Driver is 100% java.
Recital Universal ODBC Driver

Connect to remote data from Microsoft Office or other applications that support ODBC data access. The Recital Universal ODBC Driver is also available for Linux and Unix.

Key features of the Recital Universal ODBC Driver:

  • Fully Internet enabled
    The Recital Universal ODBC driver works across the internet providing access to a wide range of data sources located on remote servers running Windows, Linux, Unix and OpenVMS.
  • Works with Crystal Reports
    The Recital Universal ODBC driver supports the SQL syntax generated by Crystal Reports.
  • Works with Microsoft Office
    The Recital Universal ODBC driver works with Microsoft Office products.
  • Works with PHP on Linux
    The Recital Universal ODBC driver is available for Linux and works with PHP.
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Recital provides a wide variety of connectivity solutions to external data sources. This article provides an overview.
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In this article Barry Mavin, CEO and Chief Software Architect for Recital, gives details on Working with user-defined Functions in the Recital Database Server.

Overview

User-defined functions (UDFs) are collections of statements written in the Recital 4GL (compatible with Visual FoxPro) stored under a name and saved in a Database. User-defined functions are just-in-time compiled by the Recital database engine. User-defined functions can be used in SQL statements to extend the power and flexibility of the inbuilt functions. Using the Database Administrator in Recital Enterprise Studio, you can easily create, view, modify, and test Stored Procedures, Triggers, and user-defined functions.

Tip
You can also extend the Recital Database Server with C Extension Libraries and use the functions defined within that library also.

Creating and Editing user-defined functions

To create a new User-defined function,  right-click the Procedures node in the Databases tree of the Project Explorer and choose Create. To modify an existing User-defined function select the User-defined function in the Databases Tree in the Project Explorer by double-clicking on it or selecting Modify from the context menu. By convertion we recommend that you name your User-defined functions beginning with "f_xxx_", where xxx is the name of the table that they are associated with.

Testing the user-defined function

To test run the user-defined function, select it in the Databases Tree in the Project Explorer by double-clicking on it. Once the Database Administrator is displayed, click the Run button to run it.

Example

Example: user-defined function "f_order_details_total".
////////////////////////////////////////////////////////////////////////
// example user-defined function
function f_order_details_total(pUnitprice, pQuantity, pDiscount)
    return (pUnitprice + pQuantity + pDiscount) > 0
endfunc
Example: using the user-defined function in a SQL SELECT statement.
////////////////////////////////////////////////////////////////////////
// sample code to use a user-defined function in a SQL SELECT statement
select * from customers where f_order_details_total(Unitprice, Quantity, Discount)

Using user-defined function libraries with the Recital Database Server

You can place all of the user-defined functions associated with a particular table into a procedure library. You then define an Open Trigger for the table that opens up the procedure library whenever the table is accessed. This is a much faster way of using user-defined functions as it reduces the amount of file open/close operations during a query and also simplifies development and maintenance.

By convertion we recommend that you should name the library using the convention "lib_xxx", where xxx is the name of the table that the library is associated with.

Example: procedure library in lib_order_details.
////////////////////////////////////////////////////////////////////////
// example user-defined functions
function f_order_details_total(pUnitprice, pQuantity, pDiscount)
    return (pUnitprice * pQuantity - pDiscount) > 0
endfunc

function f_order_details_diff(pUnitprice, pQuantity, pDiscount, pValue)
    return f_order_details_total(pUnitprice, pQuantity, pDiscount) - pValue
endfunc
Example: Open Trigger in dt_order_details_open.
////////////////////////////////////////////////////////////////////////
// This trigger will open up the procedure library when the table is opened
set procedure to lib_order_details additive
Example: Close Trigger in dt_order_details_close.
////////////////////////////////////////////////////////////////////////
// This trigger will close the procedure library when the table is closed
close procedure lib_order_details
Example: using the user-defined function in a SQL SELECT statement.
////////////////////////////////////////////////////////////////////////
// sample code to use a user-defined function in a SQL SELECT statement
select * from customers where f_order_details_total(Unitprice, Quantity, Discount)

User-defined functions can also be used with any of the Client Drivers that work with the Recital Database Server.

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When stress testing our loadbalancer, i was unable to get more than 20 reliable ssh connections. The following error would be reported.

ssh_exchange_identification: Connection closed by remote host

The resolution for this is quite simple.

Edit the /etc/ssh/sshd_config file and increase the MaxStartups. On my server i set this to 200.

Edit /etc/sysctrl.conf and add the following line:

net.core.netdev_max_backlog = 3000

Then apply this change:

# sysctl -p

 

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Each Recital table can have one or more data dictionaries to provide a central repository for constraints and other metadata. 

Here's how to set up field validation for a field with a small static number of acceptable values.

Using the example.dbf table from the southwind sample database, validation can be added to the title field to ensure it matches one of a list values.
open database southwind
alter table example add constraint;
(title set check inlist(alltrim(title),"Miss","Mr","Mrs","Ms"))
The inlist() function checks whether the specified expression exists in the comma-separated list which follows.  An attempt to update title with a value not in the list will give an error: Validation on field 'TITLE' failed.

If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.

validation


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