Difference between revisions of "C-ISAM Data Files"

Revision as of 10:51, 1 December 2009

On UNIX and Linux platforms, Recital supports access to Informix compliant C-ISAM files.

Data access is achieved through a C-ISAM Bridge. This requires the creation of a Bridge file and an empty Recital table that has the same structure as the C-ISAM file.

See Also

ALTER TABLE, CREATE, CREATE BRIDGE, CREATE BRIDGE (SQL), CREATE TABLE, DISPLAY STRUCTURE, Error Messages, LIST STRUCTURE, MODIFY STRUCTURE, SELECT, USE

Creating the Recital Table

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 Workbench CREATE worksurface. 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 section for information on matching Informix and Recital data types.

Creating the Bridge File

The Bridge File can be created in two ways: using an ’ini’ file, or with the SQL CREATE BRIDGE command.

Note: The Bridge File can also be created using the CREATE BRIDGE worksurface in the Recital Workbench.

Maximums Widths

The following maximum widths apply to the bridge elements:

ini file

Firstly, an ’ini’ file should be created on the server in the data directory where the C-ISAM file is held. The ini file has the following structure:

[bridge]
bridgetype=<bridgetype>
externalname=<name of the C-ISAM file>
databasename=<name of the Recital structure table>
alias=<the name to use to access your file>

cisamdemo.ini

[bridge]
bridgetype=CISAM
externalname=cisam.dat
databasename=cisamstru.str
alias=cisamdemo

NOTE: There should be no white space either side of the ’=’ signs.

The Bridge file can now be created from the ini file. This can be given a ’.dbf’ file extension (rather than the default ’.brg’) so that it can be accessed like a normal Recital table. The SQL EXECUTE IMMEDIATE command is used to run the Recital/4GL CREATE BRIDGE FROM command:

create bridge cisamdemo.dbf from cisamdemo

CREATE BRIDGE (SQL)

The CREATE BRIDGE SQL command defines and creates the bridge in one step:

exec sql 
CREATE BRIDGE cisamdemo.dbf 
TYPE "CISAM"
EXTERNAL "cisamdemo.dat"
METADATA "cisamdemo.str"
ALIAS "cisamdemo";
 
//or
 
exec sql
CREATE BRIDGE cisamdemo.dbf
AS "TYPE=CISAM;EXTERNAL=cisamdemo.dat;METADATA=cisamdemo.str;ALIAS=cisamdemo";

Using the Bridge

The Bridge can now be used. To access the C-ISAM file, use the ’alias’ specified in the Bridge definition.

Select * from cisamdemo

Data Types