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In this article Yvonne Milne looks at the use of the Recital Remote Data Connectivity Functions with Recital Database Gateways.

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Occasionally as a Linux administrator you will be in the situation where working on a remote server and you are left with no option but to force a reboot the system. This may be for a number of reasons, but where I have found it most frequent is when working on Linux clusters in a remote location.

When the "reboot" or "shutdown" commands are executed daemons are gracefully stopped and storage volumes unmounted.
This is usually accomplished via scripts in the /etc/init.d directory which will wait for each daemon to shut down gracefully before proceeding on to the next one. This is where a situation can develop where your Linux server fails to shutdown cleanly leaving you unable to administer the system until it is inspected locally. This is obviously not ideal so the answer is to force a reboot on the system where you can guarantee that the system will power cycle and come back up. The method will not unmount file systems nor sync delayed disk writes, so use this at your own discretion.

To force the kernel to reboot the system we will be making use of the magic SysRq key.

The magic_SysRq_key provides a means to send low level instructions directly to the kernel via the /proc virtual file system.


To enable the use of  the magic SysRq option type the following at the command prompt:

 

    echo 1 > /proc/sys/kernel/sysrq

 

Then to reboot the machine simply enter the following:

 

    echo b > /proc/sysrq-trigger


Voilà! Your system will instantly reboot.
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By default Recital uses PAM to authenticate users.  It is also possible to tell PAM to use Kerberos.  Simply replace the existing entries in the /etc/pam.d/recital file with the ones below:

auth       sufficient   pam_krb5.so try_first_pass
auth       sufficient   pam_unix.so shadow nullok try_first_pass
account    required     pam_unix.so broken_shadow
account    [default=bad success=ok user_unknown=ignore] pam_krb5.so
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Platforms supported

  • Intel® / AMD™ 32 bit Linux
  • Intel® / AMD™ 64 bit Linux
  • HP PA-RISC HP-UX® 10.20 and above
  • Sun® SPARC Solaris™ 8 and above
  • HP Alpha OpenVMS 7.2-1 and above
  • SCO® OpenServer 5.0.5 and above
  • Sun® Intel® Solaris™ 10 and above
  • IBM AIX® 4.3 and above
  • HP Integrity OpenVMS 8.2-1 and above
  • HP Intel® Itanium® HP-UX® 11.23 and above
  • Mac OS X leopard 10.5 and above

Large File Support is available for Windows, Itanium HP-UX and Linux. 
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System Requirements:
  • Minimum memory: 4MB
  • Minimum Diskspace: ~20MB
The Recital Runtime System (RTS) executes the object code generated by the Recital compiler. Object files are read from disk and loaded dynamically into shared memory segments. The advantage of this is that when an application has been loaded and is being run by one user, further users share the same object code in memory. This results in performance gains, reduced memory consumption and also provides a high degree of scalability for Recital applications.
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When using Recital Web you can maintain the exact state of each cursor between pages like this.

On entry to the .rsp page.

IF type( _session["state"] ) != "U"
    m_state = _session["state"]
    RESTORE DATASESSION FROM m_state
ELSE
    // open up your tables for the first time 
ENDIF

On exit of the .rsp page.
SAVE DATASESSION TO m_state
_SESSION["state"] = m_state
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TIP
To access the menu bar in Recital, press the / key.

Full details on Recital Function Keys can be found in the Key Assist section of the Help menu, or in our documentation wiki here.
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Mac OS X leopard supports Universal Binaries so executables and dynamic libraries can be run on multiple architectures. A good example of this is the default apache install on Mac OS X. 
In order to compile apache modules for this architecture you must use the following flags when configuring the apache install.
 ./configure CFLAGS='-arch x86_64' APXSLDFLAGS='-arch x86_64' --with-apxs=/usr/sbin/apxs
Then you must pass the these additional flags to the apxs command in order to generate a Universal Binary shared module.
-Wl,-dynamic -Wl,'-arch ppc' -Wl,'-arch ppc64' -Wl,'-arch i386' -Wl,'-arch x86_64' 
-Wc,-dynamic -Wc,'-arch ppc' -Wc,'-arch ppc64' -Wc,'-arch i386' -Wc,'-arch x86_64' 
If you then do a file command on the shared module it should return; 
$ file mod_recital.so 
mod_recital2.2.so: Mach-O universal binary with 4 architectures 
mod_recital2.2.so (for architecture ppc7400): Mach-O bundle ppc 
mod_recital2.2.so (for architecture ppc64): Mach-O 64-bit bundle ppc64 
mod_recital2.2.so (for architecture i386): Mach-O bundle i386 
mod_recital2.2.so (for architecture x86_64): Mach-O 64-bit bundle x86_64
The apache module files are stored in the /usr/libexec/apache2/ directory on a default apache install on the Mac and the configuration file is /private/etc/apache2/httpd.conf
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In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to use the Client Drivers provided with the Recital Database Server to work with local or remote server-side OLE DB data sources.

Overview

The Recital Universal .NET Data Provider provides connectivity to the Recital Database Server running on any supported platform (Windows, Linux, Unix, OpenVMS) using the RecitalConnection object.

The Recital Universal JDBC Driver provides the same functionality for java applications.

The Recital Universal ODBC Driver provides the same functionality for applications that use ODBC.

Each of the above Client Drivers use a connection string to describe connections parameters.

The basic format of a connection string consists of a series of keyword/value pairs separated by semicolons. The equal sign (=) connects each keyword and its value.

The following table lists the valid names for keyword/values.


Name Default Description

Data Source
-or-
Server
-or-
Nodename

 

  The name or network address of the instance of the Recital Database Server which to connect to.
Directory   The target directory on the remote server where data to be accessed resides. This is ignored when a Database is specified.

Encrypt
-or-
Encryption

false When true, DES3 encryption is used for all data sent between the client and server.
Initial Catalog
-or-
Database
  The name of the database on the remote server.
Password
-or-
Pwd
  The password used to authenticate access to the remote server.
User ID   The user name used to authenticate access to the remote server.

Connection Pooling
-or-
Pool

false Enable connection pooling to the server. This provides for one connection to be shared.
Logging false Provides for the ability to log all server requests for debugging purposes
Rowid true When Rowid is true (the default) a column will be post-fixed to each SELECT query that is a unique row identifier. This is used to provide optimised UPDATE and DELETE operations. If you use the RecitalSqlGrid, RecitalSqlForm, or RecitalSqlGridForm components then this column is not visible but is used to handle updates to the underlying data source.
Logfile   The name of the logfile for logging
Gateway  

Opens an SQL gateway(Connection) to a foreign SQL data source on the remote server.

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)
  • ADO (Use this to connect to SQL Server and other Native Windows OLEDB data sources)
  • MySQL
  • PostgreSQL

The gateway can be specified in several formats:

servertype@nodename:username/password-database

e.g.

oracle@nodename:username/password-database

mysql@nodename:username/password-database

postgresql@nodename:username/password-database

-or-

odbc:odbc_data_source_name_on_server

oledb:oledb_connection_string_on_server

jdbc:jdbc_driver_path_on_server;jdbc:Recital:args


To connect to a server-side OLE DB data source, you use the gateway=value key/value pair in the following way.

gateway=oledb:oledb_connection_string_on_server

Important
When specifying the connection string be sure to quote the gateway= with "...".

You can find examples of connection strings for most ODBC and OLE DB data sources by clicking here.

Example in C# using the Recital Universal .NET Data Provider:
////////////////////////////////////////////////////////////////////////
// include the references below
using System.Data;
using Recital.Data;
 
////////////////////////////////////////////////////////////////////////
// The following code example creates an instance of a DataAdapter that 
// uses a Connection to the Recital Database Server, and a gateway to
// the SQL server Northwind database. It then populates a DataTable 
// in a DataSet with the list of customers. The SQL statement and 
// Connection arguments passed to the DataAdapter constructor are used 
// to create the SelectCommand property of the DataAdapter.
public DataSet SelectCustomers()
{
	string gateway = "oledb:Provider=sqloledb;Initial Catalog=Northwind;
		Data Source=localhost;Integrated Security=SSPI";
	RecitalConnection swindConn = new 
		RecitalConnection("Data Source=localhost;gateway=\""+gateway+"\");
	RecitalCommand selectCMD = new 
		RecitalCommand("SELECT CustomerID, CompanyName FROM Customers", swindConn);
	selectCMD.CommandTimeout = 30;
	RecitalDataAdapter custDA = new RecitalDataAdapter();
	custDA.SelectCommand = selectCMD;
	swindConn.Open();
	DataSet custDS = new DataSet();
	custDA.Fill(custDS, "Customers");
	swindConn.Close();
	return custDS;
}
Example in Java using the Recital Universal JDBC Driver:
////////////////////////////////////////////////////////////////////////
// standard imports required by the JDBC driver
import java.sql.*;
import java.io.*;
import java.net.URL;
import java.math.BigDecimal;
import Recital.sql.*;
 
////////////////////////////////////////////////////////////////////////
// The following code example creates a Connection to the Recital 
// Database Server, and a gateway to the SQL server Northwind database. 
// It then retrieves all the customers.
public void SelectCustomers()
{
    // setup the Connection URL for JDBC
	String gateway = "oledb:Provider=sqloledb;Initial Catalog=Northwind;
		Data Source=localhost;Integrated Security=SSPI";
	String url = "jdbc:Recital:Data Source=localhost;gateway=\""+gateway+"\";
	// load the Recital Universal JDBC Driver
	new RecitalDriver();
 
	// create the connection
	Connection con = DriverManager.getConnection(url);
	// create the statement
	Statement stmt = con.createStatement();
	// perform the SQL query
	ResultSet rs = stmt.executeQuery("SELECT CustomerID, CompanyName FROM Customers");
	// fetch the data
	while (rs.next()) 
	{
		String CompanyID = rs.getString("CustomerID");
		String CompanyName = rs.getString("CompanyName");
		// do something with the data...
	}
    
	// Release the statement
	stmt.close();
	
	// Disconnect from the server
	con.close();
}
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Recital 10 enhances the APPEND FROM command. The enhancement added the following syntax ;
APPEND FROM  TYPE CSV <file-name.csv> 
The TYPE keyword has now been enhanced to support a comma separated values (CSV) format
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