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 southwindThe 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.
alter table example add constraint;
(title set check inlist(alltrim(title),"Miss","Mr","Mrs","Ms"))
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.
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.
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USE accounts INDEX on account_no TAG outstanding FOR balance > 0 EXPLAIN SELECT * FROM accounts WHERE balance > 0 Optimized using for condition on tag 'OUTSTANDING'
Recital is a rich and versatile product with many ways to do the same thing. Developers usually write code in the way that they are accustomed to without paying much attention to how this will perform in a multi-user environment with large amounts of users and transactions. The best way to optimize Recital applications is to use the built-in tuning capabilities introduced in Recital 10.
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 |
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.
- Need to use CAT6 cables
- Slow Disk speed
- 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!
Another useful article on IBM developerworks shows how to build PHP extensions using SWIG. You can find the article here.
After split brain has been detected, one node will always have the resource in a StandAlone connection state. The other might either also be in the StandAlone state (if both nodes detected the split brain simultaneously), or in WFConnection (if the peer tore down the connection before the other node had a chance to detect split brain).
At this point, unless you configured DRBD to automatically recover from split brain, you must manually intervene by selecting one node whose modifications will be discarded (this node is referred to as the split brain victim). This intervention is made with the following commands:
# drbdadm secondary resource
# drbdadm disconnect resource
# drbdadm -- --discard-my-data connect resource
On the other node (the split brain survivor), if its connection state is also StandAlone, you would enter:
# drbdadm connect resource
You may omit this step if the node is already in the WFConnection state; it will then reconnect automatically.
If all else fails and the machines are still in a split-brain condition then on the secondary (backup) machine issue:
drbdadm invalidate resource
The Compatibility Dialog settings are written to the compat.db file in <path>/conf - please ensure that the user setting the compatibility settings has write access to this file and directory. Once these settings are written, the dialog will not be displayed unless SET COMPATIBLE is issued.