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If you want details about how storage devices are performing on Redhat/Centos/Fedora use the vmstat and iostat commands.

After installing Centos 5.3 the iostat command is not available. To install it use yum:

# yum install sysstat
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These can be found in:

/usr/include/asm-generic

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VMware products, such as ESX, Workstation, Server, and Fusion, come with a built-in VNC server to access guests.

This allows you to connect to the guest without having a VNC server installed in the guest - useful if a server doesn't exist for the guest or if you need access some time when a server would not work (say during the boot process). It's also good in conjunction with Headless Mode.

The VNC server is set up on a per-VM basis, and is disabled by default. To enable it, add the following lines to the .vmx:

RemoteDisplay.vnc.enabled = "TRUE" 
RemoteDisplay.vnc.port = "5901"

You can set a password with RemoteDisplay.vnc.key; details for how to calculate the obfuscated value given a plaintext password are in Compute hashed password for use with RemoteDisplay.vnc.key.

If you want more than one VM set up in this manner, make sure they have unique port numbers. To connect, use a VNC client pointing at host-ip-address:port. If you connect from a different computer, you may have to open a hole in the OS X firewall. If you use Leopard's Screen Sharing.app on the same computer as Fusion, don't use port 5900 since Screen Sharing refuses to connect to that.

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I was fascinated to learn that marvel are shipping a complete linux device that runs on a wall plug for less than $100. The device has gigabit ethernet and USB connectivity making it ideal for building home security and surveillance devices that can be connected together. 

This would be an ideal device for Recital Embedded. Details can be found here. Additional information can be found here and this article in Scientific American 8 Big Things to Do with a Mini Server.

Seeing as this device runs linux, nomachine can be installed on it.  

Clearly this device has a lot of uses including acting as a loadbalancer and also as a bunch of loadbalanced application servers that access data on a network using glusterfs or samba. Another great use of this device would to configure it as a rsnapshot server to backup all the machines in your home! Interestingly in quantity the device is only US$50.

Marvell have a development wiki here.
{linkr:none}
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It would appear that gigabit LAN is not! In fact it often runs at the same speed as 100Mbps LAN. Let's look at why exactly.

After configuring your network you can use the ifconfig command to see what speeds the LAN is connected. Even though 1000Mbps is reported by the card, the reality is that the overall throughtput may well be ~100Mpbs. You can try copying a large file using scp to demonstrate this.

As it turns out, in order to use a gigabit LAN you need to use CAT6 cables. CAT5 and CAT5E are not good enough. End result, the ethernet cards throttle back the speed to reduce dropped packets and errors.

You can find a good article here titled Squeeze Your Gigabit NIC for Top Performance. After tuning up the TCP parameters i found that it made no dfifference. The principal reasons behind low gigabit ethernet performance can be summed up as follows.

  1. Need to use CAT6 cables
  2. Slow Disk speed
  3. Limitations of the PCI bus which the gigabit ethernet cards use

You can get an idea about the disk speed using the hdparm command:

Display the disk partitions and choose the main linux partition which has the / filesystem.

# fdisk -l


Then get disk cache and disk read statistics:

# hdparm -Tt /dev/sda0


On my desktop system the sata disk perfomance is a limiting factor. These were the results:

/dev/sda1:
Timing cached reads:   9984 MB in  2.00 seconds = 4996.41 MB/sec
Timing buffered disk reads:   84 MB in  3.13 seconds =  58.49 MB/sec

Well, that equates to a raw disk read speed of 58.49 * 8 = 467Mbps which is half the speed of a gigabit LAN.

So.. NAS storage with lots of memory looks to be the way to go... If you use the right cables!


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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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In this article Chris Mavin, explains and details how to use the Recital Database Server with the Open Source Servlet Container Apache Tomcat.

Overview

PHP has exploded on the Internet, but its not the only way to create web applications and dynamic websites. Using Java Servlets, JavaServer Pages and Apache Tomcat you can develop web applications in a more powerful full featured Object Oriented Language, that is easier to debug, maintain, and improve.

Tomcat Installation

There are a number of popular Java application servers such as IBM Web Sphere and BEA WebLogic but today we will be talking about the use of Apache Tomcat 5, the Open Source implementation of the Java Servlet and JavaServer Pages technologies developed at the Apache Software Foundation. The Tomcat Servlet engine is the official reference implementation for both the Servlet and JSP specifications, which are developed by Sun under the Java Community Process. What this means is that the Tomcat Server implements the Servlet and JSP specifications as well or better than most commercial application servers.

Apache Tomcat is available for free but offers many of the same features that commercially available Web application containers boast.

Tomcat 5 supports the latest Servlet and JSP specifications, Servlet 2.4, and JSP 2.0, along with features such as:

  • Tomcat can run as a standalone webserver or a Servlet/JSP engine for other Web Servers.

  • Multiple connectors - for enabling multiple protocol handlers to access the same Servlet engine.

  • JNDI - The Java Naming and Domain Interface is supported.

  • Realms - Databases of usernames and passwords that identify valid users of a web application.

  • Virtual hosts - a single server can host applications for multiple domain names. You need to edit server.xml to configure virtual hosts.

  • Valve chains.

  • JDBC - Tomcat can be configured to use any JDBC driver.

  • DBCP - Tomcat can use the Apache commons DBCP for connection pooling.

  • Servlet reloading (Tomcat monitors any changes to the classes deployed within that web server.)

  • HTTP functionality - Tomcat functions as a fully featured Web Server.

  • JMX, JSP and Struts-based administration.

Tomcat Installation

In this next two sections we will walk through the install and setup of Tomcat for use with the Recital database server.

To download Tomcat visit the Apache Tomcat web site is at http://jakarta.apache.org/tomcat.
Follow the download links to the binary for the hardware and operating system you require.

For Tomcat to function fully you need a full Java Development Kit (JDK). If you intend to simply run pre compiled JavaServer pages you can do so using just the Java Runtime Environment(JRE).

The JDK 1.5 is the preferred Java install to work with Tomcat 5, although it is possible to run Tomcat 5 with JDK 1.4 but you will have to download and install the compat archive available from the Tomcat website.

For the purpose of this article we will be downloading and using Tomcat 5 for Linux and JDK 5.0, 
you can download the JDK at http://java.sun.com/javase/downloads/index.jsp.

Now we have the JDK, if the JAVA_HOME environment variable isn't set we need to set it to refer to the base JDK install directory.

Linux/Unix:
$ JAVA_HOME= /usr/lib/j2se/1.4/
$ EXPORT $JAVA_HOME
Windows NT/2000/XP:

Follow the following steps:

1. Open Control Panel.
2. Click the System icon.
3. Go to the Advanced tab.
4. Click the Environment Variables button.
5. Add the JAVA_HOME variable into the system environment variables.


The directory structure of a Tomcat installation comprises of the following:

/bin 			- Contains startup, shutdown and other scripts. 
	/common  	- Common classes that the container and web applications can use.
	/conf 		- Contains Tomcat XML configuration files XML files.
	/logs 		- Serlvet container and application logs.
	/server 		- Classes used only by the Container.
	/shared 		- Classes shared by all web application.
	/webapps 	- Directory containing the web applications.
	/work 		- Temporary directory for files and directories.

The important files that you should know about are the following:

  • server.xml

The Tomcat Server main configuration file is the [tomcat install path]\conf\server.xml file. This file is mostly setup correctly for general use. It is within this file where you specify the port you wish to be running the server on. Later in this article I show you how to change the default port used from 8080 to port 80.

  • web.xml

The web.xml file provides the configuration for your web applications. There are two locations where the web.xml file is used, 
web-inf\web.xml provides individual web application configurations and [tomcat install path]conf\web.xml contains the server wide configuration.

Setting up Tomcat for use

We'll start by changing the port that Tomcat will be listening on to 80.

To do this we need to edit [tomcat install path]/conf/server.xml and change the port attribute of the connector element from 8080 to 80.

After you have made the alteration the entry should read as:

<!-- Define a non-SSL HTTP/1.1 Connector on port 8080 -->
<Connector port="80" maxHttpHeaderSize="8192"

Next we want to turn on Servlet reloading, this will cause the web application to be recompiled each time it is accessed, allowing us to make changes to the files without having to worry about if the page is being recompiled or not.

To enable this you need to edit [tomcat install path]/conf/context.xml and change <Context> element to <Context reloadable="true">.

After you have made the alteration the entry should read as:

<Context reloadable="true">
<WatchedResource>WEB-INF/web.xml</WatchedResource>
</Context>

Next we want to enable the invoker Servlet.

The "invoker" Servlet executes anonymous Servlet classes that have not been defined in a web.xml file.  Traditionally, this Servlet is mapped to the URL pattern "/servlet/*", but you can map it to other patterns as well.  The extra path info portion of such a request must be the fully qualified class name of a Java class that implements Servlet, or the Servlet name of an existing Servlet definition.

To enable the invoker Servlet you need to edit the to [tomcat install path]/conf/web.xml and uncomment the Servlet and Servlet-mapping elements that map the invoker /servlet/*.

After you have made the alteration the entry should read as:

<servlet>
<servlet-name>invoker</servlet-name>
<servlet-class>org.apache.catalina.servlets.InvokerServlet</servlet-class>
<init-param>
<param-name>debug</param-name>
<param-value>0</param-value>
</init-param>
<load-on-startup>2</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>invoker</servlet-name>
<url-pattern>/servlet/*</url-pattern>
</servlet-mapping>

If you are you not interested in setting up your own install of Tomcat there are prebuilt versions Tomcat that has all of the above changes already made, and has the test HTML, JSP, and Servlet files already bundled. Just unzip the file, set your JAVA_HOME

Next we will give Tomcat and your web applications access to the Recital JDBC driver.

For the purposes of this article we are going to install the Recital JDBC driver in the /[tomcat install path]/common/lib/ this gives Tomcat and your web applications access to the Recital JDBC driver. The driver can be installed in a number of places in the Tomcat tree, giving access to the driver to specific application or just to the web application and not the container. For more information refer to the Tomcat documentation.

Copy the recitalJDBC.jar which is located at /[recital install path]/drivers/recitalJDBC.jar to the /[tomcat install path]/common/lib/ directory.

Linux:
$cp /[recital install path]/drivers/recitalJDBC.jar /[tomcat install path]/common/lib/
Once you have completed all the steps detailed above, fire up the server using the script used by your platform's Tomcat installation.

Linux/Unix:
[tomcat install path]/bin/startup.sh
Windows:
[tomcat install path]/bin/startup

If you are having problems configuring your Tomcat Installation or would like more detail visit the online documentation a the Apache Tomcat site.

Example and Links

Now we have setup our Tomcat installation, lets get down to it with a JSP example which uses the Recital JDBC driver to access the demonstration database (southwind) shipped with the Recital Database Server.

The example provided below is a basic JDBC web application, where the user simply selects a supplier from the listbox and requests the products supplied by that supplier.

To run the example download and extract the tar archive or simple save each of the two jsp pages individually into /[tomcat install path]/webapps/ROOT/ on your server.

By enabling the invoker Servlet earlier we have removed the need to set the example up as a web application in the Tomcat configuration files.

You can now access the example web application at http://[Server Name]/supplier.jsp if the page doesn't display, check you have followed all the Tomcat installation steps detailed earlier in this article and then make sure both Tomcat and a licensed Recital UAS are running.

Downloads:
Archive: jspExample.tar

Right click and save as individual files and rename as .jsp files:
supplier.txt details.txt

Further Reading on JSP and JDBC can be found at http://www-128.ibm.com/developerworks/java/library/j-webdata/

Final Thoughts

Recital and Apache tomcat are a powerful combination, using Java Servlet technology you can separate application logic and the presentation extremely well. Tomcat, JSP, Java Servlets and the Recital database server form a robust platform independent, easily maintained and administered solution with which to unlock the power of your Recital, Foxpro, Foxbase, Clipper, RMS and C-SAM data.

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This article discusses Recital database security: from operating system file permissions through file and field protection to DES3 encryption.

Overview

A company's data is extremely valuable and must be protected, both in operation and in physical file format. Recital products provide a range of ways to protect your data.

Operating System File Permissions

The most basic level of database security is provided by the operating system. Recital database tables and indexes are individual files with their own respective operating system file permissions. Read permission is required to open a table and write permission to update a table. If a user does not have read permission they are denied access. Without write permission, a table will be opened read-only.

Here the owner, root, and members of the recital group have write permission, so can update the example table unless additional protection applies. Other users can only open the example table read-only.

# ls -l example*
-rwxrwxr-x    1 root     recital       147 Nov 29 14:27 example.dbd
-rwxrwxr-x    1 root     recital     41580 Nov 29 14:27 example.dbf
-rwxrwxr-x    1 root     recital     13312 Nov 29 14:28 example.dbt
-rwxrwxr-x    1 root     recital     19456 Nov 29 14:28 example.dbx

Note: As in the example above, a table's associated files should have the same permissions as the table itself:

File Extension

File Type

.dbd

Dictionary

.dbf

Table

.dbt

Memo

.dbx

Index


Database Dictionary

Each Recital table may have a Database Dictionary. The Dictionary can be used both to protect the integrity of the data and to protect access to the data. This section covers Column Constraints, Triggers, Security and Protection.

Column Constraints: Data Integrity

The Dictionary attributes or constraints either prevent the entry of incorrect data, e.g. must_enter and validation or aid the entry of correct data, e.g. default, picture and choicelist. The Dictionary can be modified in the character mode CREATE/MODIFY STRUCTURE worksurface, via SQL statements, or in the Recital Enterprise Studio Database Administrator.


Click image to display full size

Fig 1: MODIFY STRUCTURE Worksurface: Dictionary.

The SQL Column Constraints are as follows:

Constraint

Description

AUTO_INCREMENT | AUTOINC

Used to auto increment the value of a column.

CALCULATED

Used to calculate the value of a column.

CHECK | SET CHECK

Used to validate a change to the value of a column.

DEFAULT

Used to set a default value for the specified column.

DESCRIPTION

Used set the column description for the specified column.

ERROR

Used to define an error message to be displayed when a validation check fails.

FOREIGN KEY

Used to define a column as a Foreign Key for a parent table.

NOCPTRANS

Used to prevent code page translation for character and memo fields.

NOT NULL | NULL

Used to disallow/allow NULL values.

PRIMARY KEY

Used to define a table’s Primary Key.

RANGE

Used to specify minimum and maximum values for a date or numerical column.

RECALCULATE

Used to force recalculation of calculated columns when a column’s value changes.

REFERENCES

Used to create a relationship to an index key of another table.

UNIQUE

Used to define the column as a candidate index for the table


These can be specified in CREATE TABLE or ALTER TABLE statements:

exec sql
  OPEN DATABASE southwind;
exec sql
  ALTER TABLE customers ADD COLUMN timeref char(8) CHECK validtime(timeref)
  ERROR "Not a valid time string";

Click image to display full size

Fig 2: Database Administrator: Column Constraints and Attributes.

TRIGGERS

Table Level Triggers are event-driven procedures called before an I/O operation. These can be used to introduce another layer of checks before a particular operation is permitted to take place or to simply set up logging of those operations.

The CREATE/MODIFY STRUCTURE worksurface <TRIGGERS> menu bar option allows you to specify table level triggers. You may edit a trigger procedure from within the <TRIGGERS> menu by placing the cursor next to the procedure name and pressing the [HELP] key. A text window pops up for editing. If the table triggers are stored in separate <.prg> files, rather than in a procedure library, procedures need not be predefined (SET PROCEDURE) before using the table.


Click image to display full size

Fig 3: MODIFY STRUCTURE Worksurface: Triggers.

 

The following triggers can be selected and associated with a specified procedure name in the <TRIGGERS> menu.

Trigger

Description

UPDATE

The specified procedure is called prior to an update operation on the table. If the procedure returns .F., then the UPDATE is canceled.

DELETE

The specified procedure is called prior to a delete operation on the table. If the procedure returns .F., then the DELETE is canceled.

APPEND

The specified procedure is called prior to an append operation on the table. If the procedure returns .F., then the APPEND is canceled.

OPEN

The specified procedure is called after an open operation on the table.

CLOSE

The specified procedure is called prior to a close operation on the table.

ROLLBACK

The specified procedure is called when a user presses the [ABANDON] key in a forms based operation.


The Recital Enterprise Studio Database Administrator also allows you to associate existing programs as Table Trigger Procedures.

Click image to display full size

Fig 4: Database Administrator: Triggers.

 

Programmatically, Trigger Procedures can also be associated with a table using SQL. The following table constraints may be applied in the SQL CREATE TABLE and ALTER TABLE statements:

Trigger

Description

ONUPDATE

The specified procedure is called prior to an update operation on the table. If the procedure returns .F., then the UPDATE is canceled.
e.g. SQL> ALTER TABLE customer modify ONUPDATE "p_update";

ONDELETE

The specified procedure is called prior to a delete operation on the table. If the procedure returns .F., then the DELETE is canceled.
e.g. SQL> ALTER TABLE customer modify ONDELETE "p_delete";

ONINSERT

The specified procedure is called prior to an insert operation on the table. If the procedure returns .F., then the INSERT is canceled.
e.g. SQL> ALTER TABLE customer modify ONINSERT "p_insert";

ONOPEN

The specified procedure is called after an open operation on the table.
e.g. SQL> ALTER TABLE customer modify ONOPEN "p_open";

ONCLOSE

The specified procedure is called prior to a close operation on the table.
e.g. SQL> ALTER TABLE customer modify ONCLOSE "p_close";

ONROLLBACK

The specified procedure is called when a user presses the [ABANDON] key in a forms based operation.
e.g. SQL> ALTER TABLE customer modify ONROLLBACK "p_rollback";


SECURITY

As mentioned above, all Recital files are subject to Operating System read and write permissions. These permissions can be further refined, while still using the Operating System user and group IDs, in the Security and Protection sections of the Dictionary. The Security section handles table based operations and the Protection section focuses on individual fields.

Security and Protection rules can be defined in the CREATE/MODIFY STRUCTURE worksurface of Recital Terminal Developer, via the SQL GRANT and REVOKE statements or in the Recital Enterprise Studio Database Administrator.

Click image to display full size

Fig 5: MODIFY STRUCTURE Worksurface: Security.

 

The Security section has table operations for which Access Control Strings can be specified. An Access Control String (ACS) is a range of valid user identification codes, and is used to restrict table operations to certain individuals or groups. Each user on the system is allocated a group number and a user number. The user identification code is the combination of group and user numbers. When constructing an Access Control String of linked user identification codes, wild card characters may be used.

Example ACS

Description

[1,2]

In group 1, user 2

[100,*]

In group 100, all users

[2-7,*]

In groups 2-7, all users

[*,100-200]

In all groups, users 100-200

[1,*]&[2-7,1-7]

In group 1, all users, in groups 2-7, users 1-7


Please note that the maximum ACS length is 254 characters. OpenVMS group and user numbers are stored and specified in octal. On other Operating Systems, group and user numbers are stored and specified in decimal.

Access Control Strings may be associated with the following operations:

Operation

Description

READONLY

Users specified in the ACS have read-only access to the table. All other users have update access.

UPDATE

Users specified in the ACS have update access to the table. All other users are restricted to read-only access.

APPEND

Users specified in the ACS can append records into the table. No other users can append.

DELETE

Users specified in the ACS can delete records from the table. No other users can delete.

COPY

Users specified in the ACS can copy records from the table. No other users can copy.

ADMIN

Users specified in the ACS can use the following commands:
SET DICTIONARY TO
MODIFY STRUCTURE
PACK
ZAP
REINDEX
All other users cannot, except the creator of the table, who is always granted ADMIN access.


The corresponding SQL privileges are:

Operation

Description

SELECT

Users specified in the ACS may name any column in a SELECT statement. All other users have update access.

UPDATE

Users specified in the ACS may name any column in an UPDATE statement. All other users are restricted to read-only access.

INSERT

Users specified in the ACS can INSERT rows into the table. No other users can INSERT.

DELETE

Users specified in the ACS can DELETE rows from the table. No other users can DELETE.

ALTER

Users specified in the ACS can use the ALTER TABLE statement on this table.

READONLY

Users specified in the ACS may read any column in a SELECT statement. All other users have update access.


// Grant insert privilege for the customer table
exec sql
  OPEN DATABASE southwind;
exec sql
  GRANT UPDATE (lastname, firstname)
  INSERT ON customers
  TO '[20,100]'; 
	
// Grant all privileges to all users
exec sql
  OPEN DATABASE southwind;
exec sql
  GRANT ALL 
  ON shippers TO PUBLIC;

PROTECTION

Security and Protection rules can be defined in the CREATE/MODIFY STRUCTURE worksurface of Recital Terminal Developer, via the SQL GRANT and REVOKE statements or in the Recital Enterprise Studio Database Administrator.

Click image to display full size

Fig 6: Database Administrator: Protection.

 


The format of the ACS is the same as in <SECURITY> above. The following protection can be defined:

Operation

Description

READONLY

Users specified in the ACS have read-only access to the field. All other users have update access.

UPDATE

Users specified in the ACS have update access to the field. All other users are restricted to read-only access.


Recital Terminal Developer also has 'HIDDEN' Protection:

Operation

Description

HIDDEN

Users specified in the ACS see the 'hiddenfield'character rather than the data in the field. All other users see the data.


Hidden fields can be accessed and viewed on a work surface, but the field contains the hiddenfield character, ‘?’. If the field is referenced in an expression, it will contain the following: blanks for character fields, ‘F’ for logical fields, 00/00/0000 for date fields and blank for memo fields.

The corresponding SQL privileges are:

Operation

Description

SELECT

Users specified in the ACS may name the column in a SELECT statement. All other users have update access.

UPDATE

Users specified in the ACS may name the column in an UPDATE statement. All other users are restricted to read-only access.

READONLY

Users specified in the ACS may read the column in a SELECT statement. All other users have update access.


// Grant update privilege for columns lastname and firstname from the customer table
exec sql
  OPEN DATABASE southwind;
exec sql
  GRANT UPDATE (lastname, firstname)
  customers TO '[20,100]';

Encryption

From Recital 8.5 onwards, Recital installations that have the additional DES3 license option have the ability to encrypt the data held in Recital database tables. Once a database table has been encrypted, the data cannot be accessed unless the correct three-part encryption key is specified, providing additional security for sensitive data.

ENCRYPT

The ENCRYPT Recital 4GL command is used to encrypt the data in the specified table or tables matching a skeleton. If the skeleton syntax is used, then all matching tables will be given the same encryption key. The encryption key is a three part comma-separated key and may optionally be enclosed in angled brackets. Each part of the key can be a maximum of 8 characters. The key is DES3 encrypted and stored in a .dkf file with the same basename as the table. After encryption, the three parts of the key must be specified correctly before the table can be accessed.

// Encrypt individual tables
encrypt customers key "key_1,key_2,key_3"
encrypt employees key "<key_1,key_2,key_3>"

// Encrypt all .dbf files in the directory
encrypt *.dbf key "key_1,key_2,key_3"
SET ENCRYPTION

If a database table is encrypted, the correct three-part encryption key must be specified before the table's data or structure can be accessed. The SET ENCRYPTION TO set command can be used to specify a default encryption key to be used whenever an encrypted table is accessed without the key being specified. The encryption key is a three part comma-separated key.

If the command to access the table includes the key, either by appending it to the table filename specification or using an explicit clause, this will take precedence over the key defined by SET ENCRYPTION TO.

Issuing SET ENCRYPTION TO without a key causes any previous setting to be cleared. The key must then be specified for each individual encrypted table.

The default key defined by SET ENCRYPTION is only active when SET ENCRYPTION is ON. SET ENCRYPTION OFF can be used to temporarily disable the default key. The SET ENCRYPTION ON | OFF setting does not change the default key itself. SET ENCRYPTION is ON by default.

// Encrypt individual tables
encrypt customers key "key_1,key_2,key_3"
encrypt shippers key "key_2,key_3,key_4"
// Specify a default encryption key
set encryption to "key_1,key_2,key_3"
// Open customers table using the default encryption key
use customers
// Specify shippers table's encryption key
use shippers<key_2,key_3,key_4>
// Disable the default encryption key
set encryption to
// Specify the individual encryption keys
use customers encryption "key_1,key_2,key_3"
use shippers<key_2,key_3,key_4>
DECRYPT

The DECRYPT command is used to decrypt the data in the specified table or tables matching a skeleton. The specified key must contain the three part comma-separated key used to previously encrypt the table and may optionally be enclosed in angled brackets. The skeleton syntax can only be used if all tables matching the skeletonhave the same key.

The DECRYPT command decrypts the data and removes the table’s .dkf file. After decryption, the key need no longer be specified to gain access to the table.

// Decrypt individual tables
decrypt customers key "key_1,key_2,key_3"
decrypt employees key "<key_1,key_2,key_3>"

// Decrypt all .dbf files in the directory
decrypt *.dbf key "key_1,key_2,key_3"

All of the following commands are affected when a table is encrypted:

  • APPEND FROM
  • COPY FILE
  • COPY STRUCTURE
  • COPY TO
  • DIR
  • USE
  • SQL INSERT
  • SQL SELECT
  • SQL UPDATE
APPEND FROM
Used to append records to the active table from another table.
// The key must be specified for an encrypted source table
use mycustomers append from customers encryption "key_1,key_2,key_3"; for country = "UK"
COPY FILE
Used to copy a file.
// The key file must also be copied for an encrypted source table
// as the target table will be encrypted
encrypt customers key "key_1,key_2,key_3" copy file customers.dbf to newcustomers.dbf copy file customers.dkf to newcustomers.dkf use newcustomers encryption "key_1,key_2,key_3"
COPY STRUCTURE
Used to copy a table's structure to a new table.
// The key file is automatically copied for an encrypted source table
// and the target table encrypted
encrypt customers key "key_1,key_2,key_3"
use customers encryption "key_1,key_2,key_3" copy structure to blankcust use blankcust encryption "key_1,key_2,key_3"
COPY TO
Used to copy a table.
// By default, the key file is automatically copied for an encrypted
// source table and the target table encrypted with the same key
encrypt customers key "key_1,key_2,key_3"
use customers encryption "key_1,key_2,key_3"
copy to newcustomers
use newcustomers encryption "key_1,key_2,key_3"

// You can also create a copy with a different key
encrypt customers key "key_1,key_2,key_3"
use customers encryption "key_1,key_2,key_3"
copy to newcustomers encrypt "newkey_1,newkey_2,newkey_3"
use newcustomers encryption "newkey_1,newkey_2,newkey_3"

// Or create a decrypted copy
encrypt customers key "key_1,key_2,key_3"
use customers encryption "key_1,key_2,key_3"
copy to newcustomers decrypt
use newcustomers

// You can also create an encrypted copy of a non-encrypted source table
use orders
copy to encorders encrypt "newkey_1,newkey_2,newkey_3"
use encorders encryption "newkey_1,newkey_2,newkey_3"
DIR
Used to display a directory listing of tables.
// Encrypted tables are flagged as such with (DES3)
> open database southwind
> dir
Current database: southwind
Tables				# Records		Last Update	Size		Dictionary	Triggers	Security
categories.dbf			8			01/10/06		24576	None		None		None
cisamdemo.dbf       ---> CISAM/Bridge        [cisamdemo]
customers.dbf (DES3)		91			05/12/04		49600	None		None		None
employees.dbf			9			05/12/04		25520	None		None		None
example.dbf   (DES3)		100			12/24/05		38080	Yes		Yes		None
order_details.dbf			2155			05/12/04		296320	None		None		None
orders.dbf				829			05/12/04		232704	None		None		None
products.dbf			77			05/12/04		37112	None		None		None
productsbyname.dbf		77			05/12/04		29104	None		None		None
shippers.dbf  (DES3)		3			05/12/04		20864	None		None		None
suppliers.dbf			29			12/08/05		29992	Yes		None		None

   0.765 MB in 11 files.
   1.093 GB remaining on drive.
USE
Used to open a table.
// The three part key must be specified to open an
// encrypted table.  All of the following are valid.
// 1. Specifying a default encryption key before opening the table
set encryption to "key_1,key_2,key_3"
use customers
// 2. Appending the key to the filename
use customers<key_1,key_2,key_3>
// 3. Using the ENCRYPTION clause, optionally specifying angled brackets
use customers encryption "key_1,key_2,key_3"
use customers encryption "<key_1,key_2,key_3>"
SQL INSERT
Used to add a row to a table via SQL.
// The three part key can be specified using a
// default encryption key before opening the table
exec sql
  OPEN DATABASE southwind;
exec sql
  SET ENCRYPTION TO "key_1,key_2,key_3";
exec sql
  INSERT INTO customers
  (customerid, companyname)
  VALUES
  ('RECIT','Recital Corporation');
// Or by appending the key to the filename
exec sql
  OPEN DATABASE southwind;
exec sql
  INSERT INTO customers<key_1,key_2,key_3>
  (customerid, companyname)
  VALUES
  ('RECIT','Recital Corporation');
SQL SELECT
Used to return data from a table via SQL.
// The three part key can be specified using a
// default encryption key before opening the table
exec sql
  OPEN DATABASE southwind;
exec sql
  SET ENCRYPTION TO "key_1,key_2,key_3";
exec sql
  SELECT * FROM customers;
// Or by appending the key to the filename
exec sql
  OPEN DATABASE southwind;
exec sql
  SELECT * FROM customers<key_1,key_2,key_3>;
SQL UPDATE
Used to update data in a table via SQL.
// The three part key can be specified using a
// default encryption key before opening the table
exec sql
  OPEN DATABASE southwind;
exec sql
  SET ENCRYPTION TO "key_1,key_2,key_3";
exec sql
  UPDATE customers
  SET companyname='Recital Corporation Inc.'
  WHERE customerid='RECIT';
// Or by appending the key to the filename
exec sql
  OPEN DATABASE southwind;
exec sql
  UPDATE customers<key_1,key_2,key_3>
  SET companyname='Recital Corporation Inc.'
  WHERE customerid='RECIT';

Summary

Recital offers a range of ways to keep your data secure. These start with the Operating System read/write permissions, which can be further refined to the level of table I/O operations and then field access in the Dictionary based Security and Protection rules. The Dictionary also provides the means to protect the integrity of the data via data validation and to assist in correct data entry through the use of choicelists, help messages and picture clauses etc. A further role of the Dictionary is in the provision of Table Triggers, which can be used to enable a programmatic response to table operations to add in additional checks or audit trails. For the most sensitive data, DES3 encryption is the ultimate protection: encrypting the physical data on the disk and only permitting table access on the production of the three part encryption key.

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STRERROR()

Syntax

STRERROR( [ <expN> ] )

Description

The STRERROR() function returns a string describing the last operating system error message. If the optional error number is specified then the related operating system error message will be returned.

Example

mqdes=mqcreate("/myqueue", 2)
 if (mqdes < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 rc = mqsend(mqdes, "Test message")
 if (rc < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 mqclose(mqdes)

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Recital 10 introduced the DIE( )and EXIT( ) functions. These functions operates in the same way as the PHP DIE( ) and EXIT( ) functions. They output a message and terminate the current session in both Recital and Recital Web.
try
  open database southwind
catch
  die("Cannot open database, please try later.")
endtry
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