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SE Linux is a feature of the Linux kernel that provides mandatory access control. This policy based access control system grants far greater control over the resources on a machine than standard Linux access controls such as permissions.

Many modern Linux distributions are shipping with SELinux enabled by default, Fedora 14 and Rhel 6 both install with it enabled.

When you run Recital Web on a SELinux enabled machine and navigate to the default.rsp page you will see something similar to the screen shot below.

1
If you launch the SELinux troubleshooter you will see the following problem.

SELinux is blocking the apache server from accessing the Recital server running on port 8001.

2
To manage you SELinux policy you must have the policycoreutils package group installed. The policycoreutils contains the policy core utilities that are required for basic operation of a SELinux system.

If you wish to use a GUI tool, you must install the policycoreutils-gui package.

At the command prompt execute the following:

As root

$ yum install policycoreutils

$ semanage port -a -t http_port_t -p tcp 8001

$ service recital restart

$ service httpd restart 
 

We use the semanage command here to allow the http server access to port 8001. Once you have completed the steps detailed above you can go and navigate back to the default.rsp page in your borwser, where you will find the permission denied message is now replaced by the default.rsp page.


4
SELinux does a great job of restricting services and daemons so rather than simply disabling it, why not work with it!

When it comes to security, every little bit helps...

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Found a nice subversion plugin for finder on the MAC.

The goal of the SCPlugin project is to integrate Subversion into the Mac OS X Finder. 

  • Support for Subversion.
  • Access to commonly used source control operations via contextual menu [screenshot]
  • Dynamic icon badging for files under version control. Shows the status of your files visually. [ screenshot ]
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A number of people have complained about data loss after a system crash when using Ext4.  A bug report was logged. According to multiple posts by a developer of Ext4, Theodore Tso, this is due to differences in approach to security and performance issues between the two file systems.

Ext3 commits writes to disk within approximately 5 seconds - Ext4 can take from 40-150 seconds.  In addition, if a system is using Ext3 and crashes before the commit takes place you will still have the previous contents of a file where under Ext4 the file will be empty.  Theodore Tso feels that this is a failure at the application level and that the file system is behaving as designed and as specified by the POSIX spec (which apparently does not specify what is supposed to happen when a system is not shut down cleanly).  His solution to the issue is to suggest proper use of fsync() and lists various scenarios/examples in post 54 of the bug report (linked above).  In addition he wrote a patch that recognize the rename() situation mentioned in his post 54 yet retains the normal Ext4 behaviors and performance in the majority of cases.  Also a more "proper" solution has been provided which allows the behavior of Ext3 to be retained under Ext4 by mounting it with alloc_on_commit.

A somewhat related topic is the use of on-board caching by hard drives.  This behavior can be modified on most drives by using hdparm.
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A good article describing the configuration of samba for file/record locking can be found here.

Basically you must add these directives to the smb.conf file:

[data] 
oplocks = False 
level2 oplocks = False

The default oplock type is Level1. Level2 oplocks are enabled on a per-share basis in the smb.conf file. Alternately, you could disable oplocks on a per-file basis within the share: 

veto oplock files = /*.dbf/*.DBF/*.ndx/*.NDX/*.dbx/*.DBX/*.dbt/*.DBT/

You can further tune samba by following this guide.

If you specify the Common Internet File System (CIFS) when you mount the samba share then you must specify the following options
mount -t cifs {mount-point} -o username=name,pass=pass,directio
The directio option is used to not do inode data caching on files opened on this mount. This precludes mmaping files on this mount. In some cases with fast networks and little or no caching benefits on the client (e.g. when the application is doing large sequential reads bigger than page size without rereading the same data) this can provide better performance than the default behavior which caches reads (readahead) and writes (writebehind) through the local Linux client pagecache if oplock (caching token) is granted and held. Note that direct allows write operations larger than page size to be sent to the server.

If you get the following error when trying to mount the {mount-point}
Apr 22 16:57:39 bailey kernel: Status code returned 0xc000006d NT_STATUS_LOGON_FAILURE
Apr 22 16:57:39 bailey kernel:  CIFS VFS: Send error in SessSetup = -13
Apr 22 16:57:39 bailey kernel:  CIFS VFS: cifs_mount failed w/return code = -13
The you need to create the Samba user specified on the mount command
smbpasswd -a username
FYI - Make sure you umount all the Samba {mount-point(s)} before shutting down Samba.
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Recital 10 enhances the APPEND FROM command. The enhancement was added to the following syntax ;
APPEND FROM  <table-name> 
Before when appending into a shared Recital table each new row was locked along with the table header, then unlocked after it was inserted. This operation has now been enhanced to lock the table once, complete inserting all the rows from the table and then unlock the table. The performance of this operation has been increased by using this method. All the database and table constraints are still enforced.
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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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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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Recital 10 introduced the REQUIRE() and REQUIRE_ONCE() statement.

The REQUIRE() statement includes and executes the contents of the specified file at the current program execution level.

When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables, procedures, functions or classes declared in the included file will be available at the current program execution level.

The REQUIRE_ONCE() statement is identical to the REQUIRE() statement except that Recital will check to see if the file as already been included and if so ignore the command.

The full syntax is:
REQUIRE( expC )
REQUIRE_ONCE( expC )

e.g.

REQUIRE_ONCE( "myapp/myglobals.prg" )
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To insert code samples into your articles in joomla, you use the pre tag like this:

<pre xml:lang="xxx"> your code goes here </pre>

You can use any of the following languages for colorizing your code in articles. 
 

recital, abap, dos, lotusscript, rails, actionscript3, dot, lscript, reg, actionscript, d, lua, robots, ada, eiffel, m68k, ruby, apache, email, make, sas, applescript, fortran, matlab, scala, apt_sources, freebasic, mirc, scheme, asm, genero, mpasm, scilab, asp, gettext, mxml, sdlbasic, autoit, glsl, mysql, smalltalk, avisynth, gml, nsis, smarty, bash, gnuplot, objc, sql, basic4gl, groovy,

ocaml-brieftcl, bf, haskell, ocaml, teraterm, blitzbasic, hq9plus, oobas, text, bnf, html4strict, oracle11, thinbasic, boo, idl, oracle8, tsql, caddcl, index.html, pascal, typoscript, cadlisp, ini, perl, vbnet, cfdg, inno, per, vb, cfm, intercal, php-brief, verilog, cil, io, php, vhdl, c_mac, java5, pic16, vim, cobol, java, pixelbender, visualfoxpro, c, javascript, plsql, visualprolog, cpp, kixtart, povray, whitespace, cpp-qt, klonec, powershell, winbatch, csharp, klonecpp, progress, xml, css, latex, prolog, xorg_conf, delphi, lisp, providex, xpp, diff, lolcode, python, z80, div, lotusformulas, qbasic

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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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