Kbase 7260: Overview to C-ISAM Gateway: Compatibility, Features 1-/95
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
5/10/1998 |
|
Overview to C-ISAM Gateway: Compatibility, Features 1-/95
920229-elp01
THE PROGRESS C-ISAM GATEWAY
INTRODUCTION:
=============
This Progress Software Technical Support Knowledgebase
Entry decsribes the PROGRESS C-ISAM Gateway, which enables
users to develop 4GL applications which access and
update data within existing C-ISAM files. In this way,
PROGRESS applications can be integrated and easily
share data with C-ISAM based application. The gateway
also offers a solution to users who need a gradual
migration path from older 3GL/ISAM technology to newer
4GL/RDBMS technology.
PROCEDURAL APPROACH:
====================
ENVIRONMENT. The PROGRESS C-ISAM Gateway is an
interface into a logical PROGRESS database
made up of two parts: the C-ISAM files and a PROGRESS
RDBMS schema holder database. The PROGRESS development
tools and existing applications interface with the gateway
product and the schema holder, as illustrated below.
********************* *****************
* C-ISAM GATEWAY * <----------- * PROGRESS 4GL *
********************* *****************
/|\ /| | |
+ - - - - | - - - - - - - - - - - - - - - -|- - - - -+
| \|/ \|/ |
| ***************** ****************** |
| * C-ISAM FILES * * PROGRESS RDBMS * |
| ***************** * SCHEMA HOLDER * |
| /|\ ****************** |
| | {Logical PROGRESS database} |
+ - -|- - - - - - - - - - - - - - - - - - - - - - - -+
|
\|/
*********************
* Existing C-ISAM *
* Applications *
*********************
BACKGROUND. C-ISAM is an index file management system
developed and sold by Informix Software. It offers a
basic B-tree access method, and supports multiple
indexes, file and record locking, and transactions. It
is provided as a series of C library routines which
implement these functions. C-ISAM is a file manager,
not a database, so it has no data dictionary.
Although originally developed for UNIX systems, C-ISAM
has been ported by Informix to DOS and OS/2. PROGRESS
has no plans at this time to support direct access to
local C-ISAM files on DOS, WINDOWS, or OS/2.
C-ISAM has become the ISAM (Indexed Sequential Access
Method) standard for UNIX systems. It is included as
part of X/Open's XPG3 specification and as an optional
component of UNIX V.4 (re-licenses from Informix by
AT&T). C-ISAM is provided by the systems vendor or
directly from Informix for all UNIX-based systems.
Some vendors have opted to clone C-ISAM. Sometimes
when users indicate that they are using C-ISAM, they
are actually using a clone; in general the clones
appear to be highly compatible. Sun has developed a
partial-clone called NetISAM, which adds the ability
for C-ISAM applications to remotely access a C-ISAM
file, however, it has an incompatible file format.
The PROGRESS C-ISAM Gateway:
- Allows PROGRESS applications to run concurrently
with existing C-ISAM applications.
- Supports C-ISAM standards for locking and
transaction control.
- Automatically captures index format information
from the C-ISAM fies; field defintions and
validation criteria can be applied in the PROGRESS
Data Dictionary.
- Supports all standard C-ISAM data formats and
provides flexibility in supporting non-standard
formats, including: null-terminated character
strings, native 16- and 32-bit integers, dates, raw
data, logicals, and arrays.
- Supports all Micro Focus COBOL II and Informix SE
data formats.
Portability:
- Via standard PROGRESS distributed database
capabilities, C-ISAM data may be accessed
concurrently with PROGRESS databases in the same
transaction.
- PROGRESS applications written for C-ISAM can run
on the PROGRESS RDBMS without modification.
COMPATIBILITY. The PROGRESS C-ISAM Gateway is
compatible with Version 4 of the standard
Informix C-ISAM product and with NetISAM on the
Sun Sparc. Progress has no current plans to do
QA testing of other clone products. The other major
COBOL vendors on UNIX, Ryan McFarland and Accucobol,
use proprietary ISAM file formats which are not
supported by the gateway.
Starting with PROGRESS Version 6.3D, commercially shipping beginning
September 1993, we will provide support for both Version 4.0 and
Version 5.0 of INFORMIX C-ISAM. Customers using C-ISAM 5.0 with
PROGRESS 6.2 should contact Technical Support to confirm availability
of a non-commercial patch for the specific platform involved.
PROGRESS C-ISAM DataServer products in 6.2L, 6.3B and 6.3C are
incompatible with Informix C-ISAM 5.0.
The C-ISAM Gateway supports nearly all PROGRESS 4GL
syntax except for SETUSERID and RECID, including FIND
PREV. See the "Database Gateways Guide" for other
minor differences. Both FAST TRACK and RESULTS
will run with the C-ISAM Gateway.
REFERENCES TO WRITTEN DOCUMENTATION:
====================================
Gateways Guide, 1992 edition.
MarketWatch (updated May 1993)
MarketWatch (updated August 1993)
There is a limit of the number of C-ISAM files you can have open at
any one time. That number is 64. PROGRESS gives a generic error
message that pointed to the fact that we were running out of open
files. The error received is 2172.
Progress Software Technical Support Note # 7260