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.
FOREACH array_expression AS value
statements...
ENDFOR
FOREACH array_expression AS key => value
statements...
ENDFOR
The first form loops over the array given by array_expression. On each loop, the value of the current element is assigned to value and the internal array pointer is advanced by one (so on the next loop, you'll be looking at the next element). The second form does the same thing, except that the current element's key will be assigned to the variable key on each loop. This form works only on associative arrays and objects.


I am a fan of the previous incarnation of the PlugComputer so I was excited to see that Marvell have unveiled a new PlugComputer dubbed imaginatively "PlugComputer 3.0."
PlugComputer 3.0 Features:
Smaller sleeker design,
More powerful CPU - 2gz Armanda 300 CPU,
120GB 1.8-inch SATA hard drive,
Wifi,
Bluetooth,
10/100/1000 wired Ethernet,
USB 2.0.
512MB of RAM
512MB of Flash memory
I for one would like to see an additional Ethernet port added to increase application flexibility, for some applications where you are using clustered plugs or even for routing, having multiple Ethernet ports is a must.
Even without multiple ethernet ports, these low power consumption devices really could have a place in SME environments, replacing large cumbersome legacy hardware with compact Linux plug servers.
More information about the PlugComputer can be found here
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.
Opening SSH to the outside world is a security risk. Here is how to restrict SSH access to certain IP addresses on a machine.
- Edit the /etc/hosts.allow file to include these lines, assuming your machine is on the 192.168.2.x nonrouting IP block, and you want to enable an external address of 217.40.111.121 IP block: Remember to add the period on the end of each incomplete IP number. If you have another complete IP address or range, add a space and that range on the end.
sshd,sshdfwd-X11: 192.168.2. 217.40.111.121
- Edit your /etc/hosts.deny file to include this line:
sshd,sshdfwd-X11:ALL
- These lines refuse SSH connections from anyone not in the IP address blocks listed.
Additionally you can restrict SSH access by username.
- Edit the /etc/ssh/sshd_config file and add the following lines
PermitRootLogin no
AllowUsers user1 user2 user3 etc
PasswordAuthentication yes
Now restart the ssh daemon for these changes to take effect
service sshd restart
There is a good article on the gluster website here which gives some good information regarding file system optimization suitable for a HA Recital cluster solution.
This article looks at the range of client access mechanisms for Windows that can be used with the Recital C-ISAM Bridge and details bridge configuration and usage.
Overview
Just because the format of data is regarded as 'legacy' does not make that data in any way obsolete. Modern client interfaces can not only extend the life of long-term data, but also provide different ways to analyse and gain advantage from that data.
Recital Corporation provides a range of solutions to interface to Informix compliant C-ISAM data on Linux or UNIX from Windows clients.
.NET
Click image to display full size
Fig 1: Recital Mirage .NET application accessing the C-ISAM Demo table.
Recital offers two alternative ways to access C-ISAM data using Microsoft .NET:
The Recital .NET Data Provider is a managed Data Provider written in C# that provides full compatibility with the Microsoft SQLserver and OLE DB data providers that ship with the .NET framework. It is fully integrated with the Visual Studio .NET IDE supporting data binding and automatic code generation using the form designer. The Recital .NET Data Provider works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
Recital Mirage .NET is a complete solution for migrating, developing and deploying 4GL database applications. Recital Mirage .NET works in conjunction with the Recital Mirage .NET Application Server for Linux or UNIX to access C-ISAM data.
JDBC
Click image to display full size
Fig 2: Java™ Swing JTable accessing the C-ISAM Demo table via the Recital JDBC Driver.
The Recital JDBC Driver is an all Java Type 4 JDBC 3.0 Driver, allowing you to access C-ISAM data from Java applets and applications. The Recital JDBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
ODBC
Click image to display full size
Fig 3: Microsoft® Office Excel 2003 Pivot Chart and Pivot Table accessing the C-ISAM Demo table via the Recital ODBC Driver.
The Recital ODBC Driver is an ODBC 3.0 Driver, allowing you to access C-ISAM data from your preferred ODBC based Windows applications. You can develop your own applications in languages such as C++ or Visual Basic, manipulate the data in a spreadsheet package or word processor document and design charts, graphs and reports. The Recital ODBC Driver works in conjunction with the Recital Database Server for Linux or UNIX to access C-ISAM data.
Configuring the Recital C-ISAM Bridge
Data access is achieved through a C-ISAM Bridge. This requires the creation of an empty Recital table that has the same structure as the C-ISAM file and of a RecitalC-ISAM Bridge file.
On Linux and UNIX, Recital Terminal Developer and the Recital Database Server come complete with an example C-ISAM data file, C-ISAM index and Recital C-ISAM bridge that can be used for testing and as a template for configuring your own C-ISAM bridges. The Recital Database Server also includes a bridge creation ini file.
Step 1:
Create a Recital table with the same structure as the C-ISAM file. The fields/columns in the structure file must exactly match the data type and length of those in the C-ISAM file. The Recital table will have one byte more in total record length due to the Recital record deletion marker.
To create the table, use the SQL CREATE TABLE command or the Recital Terminal Developer CREATE worksurface. The SQL CREATE TABLE command can be called directly:
SQLExecDirect:
In: hstmt = 0x00761BE8,
szSqlStr = "CREATE TABLE cisamdemo.str (DD Char(4)
DESCRIPTION "Dd...", cbSqlStr = -3
Return: SQL_SUCCESS=0
or be included in a 4GL program:
// createtab.prg
CREATE TABLE cisamdemo.str;
(DD Char(4) DESCRIPTION "Dd",;
CONFIRM Char(6) DESCRIPTION "Confirm",;
PROCDATE Char(6) DESCRIPTION "Procdate",;
CONTROL Char(5) DESCRIPTION "Control",;
DOLLARS Decimal(13,2) DESCRIPTION "Dollars",;
DEALER Char(5) DESCRIPTION "Dealer",;
TERRITORY Char(2) DESCRIPTION "Territory",;
WOREP Char(12) DESCRIPTION "Worep",;
CURRTRAN Char(3) DESCRIPTION "Currtran",;
TRADDATE Char(6) DESCRIPTION "Traddate",;
CITY Char(10) DESCRIPTION "City",;
ACCOUNT Char(11) DESCRIPTION "Account",;
PRETRAN Char(2) DESCRIPTION "Pretran",;
AFSREP Char(14) DESCRIPTION "Afsrep",;
REPKEY Char(9) DESCRIPTION "Repkey",;
BRANCH Char(3) DESCRIPTION "Branch",;
WODEALER Char(5) DESCRIPTION "Wodealer",;
BANKCODE Char(2) DESCRIPTION "Bankcode",;
COMMRATE Decimal(6,4) DESCRIPTION "Commrate",;
NEWREP Char(1) DESCRIPTION "Newrep",;
SETTLE Char(1) DESCRIPTION "Settle",;
POSTDATE Char(6) DESCRIPTION "Postdate")
if file("cisamdemo.str")
return .T.
else
return .F.
endif
// end of createtab.prg
Server-side 4GL programs can be called by all clients, e.g. from a Java class with a JDBC connection:
//---------------------------------
//-- create_str.java --
//---------------------------------
import java.sql.*;
import java.io.*;
import Recital.sql.*;
public class create_str {
public static void main(String argv[]) {
try {
new RecitalDriver();
String url = "jdbc:Recital:" +
"SERVERNAME=cisamserver;" +
"DIRECTORY=/usr/recital/data/southwind;" +
"USERNAME=user;" +
"PASSWORD=password";
Connection con = DriverManager.getConnection(url, "user", "pass");
Statement stmt = con.createStatement();
CallableStatement sp = con.prepareCall("{call createtab}");
boolean res = sp.execute();
String outParam = sp.getString(1);
System.out.println("Returned "+outParam);
sp.close();
con.close();
} catch (Exception e) {
System.out.flush();
System.err.flush();
DriverManager.println("Driver exception: " + e.getMessage());
e.printStackTrace();
}
try {
System.out.println("Press any key to continue...");
System.in.read();
} catch(IOException ie) {
;
}
}
}
The table should be given a ‘.str’ file extension (rather than the default ‘.dbf’) to signify that this is a structure file only.
Please see the end of this article for information on matching Informix and Recital data types

Fig 4: Recital CREATE/MODIFY STRUCTURE worksurface for character mode table creation.
Step 2: Creating the Bridge File
If you have Recital installed on the server platform, the Bridge File can be created using the CREATE BRIDGE worksurface. The corresponding command to modify the bridge file is MODIFY BRIDGE <bridge file>. This is the cisamdemo.dbf bridge file in the CREATE/MODIFY BRIDGE WORKSURFACE:
> modify bridge cisamdemo.dbf

Fig 5: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface for bridge creation.
For Recital Database Server clients, the Bridge File can be created using the Recital/SQL CREATE BRIDGE command:
Recital/SQL CREATE BRIDGE:
CREATE BRIDGE cisamdemo.dbf; TYPE "CISAM"; EXTERNAL "cisamdemo.dat"; METADATA "cisamdemo.str"; ALIAS "cisamdemo"
or:
CREATE BRIDGE cisamdemo.dbf; AS "type=CISAM;external=cisamdemo.dat;metadata=cisamdemo.str;alias=cisamdemo"
The examples above assume that the C-ISAM file, the bridge file and the Recital structure file are all in the current working directory. Full path information can be specified for the <externalname> and the <databasename>. For added flexibility, environment variables can be used to determine the path at the time the bridge is opened. Environment variables can be included for either or both the <externalname> and the <databasename>. A colon should be specified between the environment variable and the file name.
e.g.
CREATE BRIDGE cisamdemo.dbf; TYPE "CISAM"; EXTERNAL "DB_DATADIR:cisamdemo"; METADATA "DB_MIRAGE_PATH:cisamdemo.str"; ALIAS "cisamdemo"
Recital CREATE BRIDGE/MODIFY BRIDGE worksurface:

Fig 6: Recital CREATE BRIDGE/MODIFY BRIDGE worksurface - using environment variables.
Using the Bridge
The Bridge can now be used. To access the C-ISAM file, use the ‘alias’ specified in the Bridge definition.
SQL:
SELECT * FROM cisamdemo
Recital/4GL:
use cisamdemo
Indexes
The cisamdemo.dat file included in the Recital distributions for Linux and UNIX has three associated index keys in the cisamdemo.idx file:
Select area: 1 Database in use: cisamdemo Alias: cisamdemo Number of records: 4 Current record: 2 File Type: CISAM (C-ISAM) Master Index: [cisamdemo.idx key #1] Key: DD+CONFIRM+PROCDATE+CONTROL Type: Character Len: 21 (Unique) Index: [cisamdemo.idx key #2]
Key: DD+SUBSTR(CONFIRM,2,5)+TRADDATE+STR(DOLLARS,13,2) +CURRTRAN+ACCOUNT Type: Character Len: 42 Index: [cisamdemo.idx key #3] Key: DEALER+BRANCH+AFSREP+SUBSTR(PROCDATE,5,2) +SUBSTR(CONTROL,2,4) Type: Character Len: 28
The Recital C-ISAM bridge makes full use of the C-ISAM indexes. SQL SELECT statements with WHERE clauses are optimized based on any of the existing indexes when possible. The following ODBC SELECT call makes use of key #3 rather than sequentially searching through the data file.
SQLExecDirect:
In: hstmt = 0x00761BE8,
szSqlStr = "select * from cisamdemo
where dealer+branch+afsrep=' 00161 595-7912",
cbSqlStr = -3
Return: SQL_SUCCESS=0
Get Data All:
"DD", "CONFIRM", "PROCDATE", "CONTROL", "DOLLARS", "DEALER",
"TERRITORY", "WOREP", "CURRTRAN", "TRADDATE", "CITY", "ACCOUNT",
"PRETRAN", "AFSREP", "REPKEY", "BRANCH", "WODEALER", "BANKCODE",
"COMMRATE", "NEWREP", "SETTLE", "POSTDATE"
"0159", " 15522", "930312", "13356", 4992.60, "00161", "19",
"", "210", "930305", "", "70000100009", "", "595-7912",
"930315791", "", "", "59", 0.0000, "1", "", "930315"
1 row fetched from 22 columns.
Using the Recital/4GL, the primary index is set as the master index when the bridge is first opened. Any secondary indexes can be selected using the SET ORDER TO <expN> command. The Recital/4GL SEEK or FIND commands and SEEK() function can be used to search in the current master index.
> SET ORDER TO 3 Master index: [cisamdemo.idx key #3] > SEEK “00161 595-7912”
Appendix 1: Data Types
|
Informix |
Recital |
|
Byte |
Numeric |
|
Char |
Character |
|
Character |
Character |
|
Date |
Date |
|
Datetime |
Character |
|
Decimal |
Numeric |
|
Double Precision |
Float |
|
Float |
Real |
|
16 Bit Integer |
Short |
|
Integer |
Numeric |
|
Interval |
Character |
|
32 Bit Long |
Integer |
|
Money |
Numeric |
|
Numeric |
Numeric |
|
Real |
Numeric |
|
Smallfloat |
Numeric |
|
Smallint |
Numeric |
|
Text |
Unsupported |
|
Varchar |
Character |
Appendix 2: C-ISAM RDD Error Messages
The following errors relate to the use of the Recital CISAM Replaceable Database Driver (RDD). They can be received as an ‘errno <expN>’ on Recital error messages:
|
ERRNO() |
Error Description |
|
100 |
Duplicate record |
|
101 |
File not open |
|
102 |
Invalid argument |
|
103 |
Invalid key description |
|
104 |
Out of file descriptors |
|
105 |
Invalid ISAM file format |
|
106 |
Exclusive lock required |
|
107 |
Record claimed by another user |
|
108 |
Key already exists |
|
109 |
Primary key may not be used |
|
110 |
Beginning or end of file reached |
|
111 |
No match was found |
|
112 |
There is no “current” established |
|
113 |
Entire file locked by another user |
|
114 |
File name too long |
|
115 |
Cannot create lock file |
|
116 |
Memory allocation request failed |
|
117 |
Bad custom collating |
|
118 |
Duplicate primary key allowed |
|
119 |
Invalid transaction identifier |
|
120 |
Exclusively locked in a transaction |
|
121 |
Internal error in journaling |
|
122 |
Object not locked |
One of the attractive features of Linux is the impressive 3D desktop that even works on most older hardware.
You can enabled the 3D Desktop on CentOS5 by installing the compiz package:
yum install compiz
After you have done this, go to the top panel and click System, then select Preferences > and click 'Desktop Effects.
You will get a new dialog. To test and see if your hardware supports the 3D Desktop, press the button Enable Desktop Effects. If everything works fine, you can select Keep Settings.
Then test your 3D Desktop by pressing Ctrl-Alt-Left and Ctrl-Alt-Right, or drag a window around or even out of the screen to the left or right. If you maximize a window, you will see another cool effect. If you move the mouse to the upper-right corner of the screen you see all your opened applications.Way cool!
Yes, your FoxPlus and FoxPRO applications should run under Recital with little to no changes at all. We provide expert product support if you have any questions or problems. If you lack the resources to move your applications into Recital we can provide that service to you also if required.