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Informix Error -854: Back end not found. Or back end is busy.

Cause and resolution

Back end not found. Or back end is busy.

In DOS, the application cannot establish a connection to the local IBM Informix SE engine or to the IBM Informix NET PC communications module.

The SE engine (for accessing a local database) or the IBM Informix NET PC communications module (for accessing a remote database) must be loaded before trying to connect to it by means of, for example, a DATABASE statement. To load the SE engine, run PSTARTSQ. To load the IBM Informix NET PC communications module, run REMSQL.

If the SE engine or the IBM Informix NET PC communications module has previously been loaded, and you get this error message, either another application currently has a connection to the SE engine, or the IBM Informix NET PC communications module (they can have only one connection at a time), or the current application encountered an internal error and lost the connection.

If another application has a connection to the SE engine or to the IBM Informix NET PC communications module, you must first release that connection before you can connect the current application. If the other application is a 4GL or an ESQL/C program, that application releases its connection by executing a CLOSE DATABASE statement, calling the SQLEXIT( ) function, or exiting.

In extreme situations where an internal error has occurred, you must exit the application and stop the SE engine or the IBM Informix NET PC communications module from the DOS command line. To stop the SE engine, run PSTARTSQ with the -T option. After you stop the SE engine, run PSTARTSQ with no options to reload it. To stop the IBM Informix NET PC communications module, run SETNET with the -T option. After you stop the IBM Informix NET PC communications module, run REMSQL to reload it.

This error message also might appear when a client Windows application uses the wrong .DLL file to connect to a database server across a network. Client Windows applications that work with IBM Informix NET PC Version 4.1 (such as Version 4.1 ESQL/C) can also work with IBM Informix NET for Windows Version 5.01. Check to see whether IBM Informix NET PC Version 4.1 and IBM Informix NET for Windows Version 5.01 reside on the same client computer concurrently. If so, check that Version 5.01 of the LDLLSQLW.DLL file appears in your PATH environment variable setting before Version 4.1 of the LDLLSQLW.DLL file. In addition, Version 4.1 of the LDLLSQLW.DLL file must not reside in the current directory, the Windows directory, the Windows \SYSTEM directory, or the directory that contains the executable file of the application that you are running.

Oninit® Troubleshooting Guidance

Reasons / Common Causes

-854 is specific to older DOS-based IBM Informix SE / Informix NET PC deployments: it fires when the application can't establish a connection to the local SE engine, or to the Informix NET PC communications module (for remote access) — per the official guidance, either the engine/module was never loaded, or it's already in use by another application (each supports only one connection at a time), or the current application had an internal error and lost its connection.

  1. The SE engine (or NET PC communications module) never loaded, per the official guidance — needs to be started before any connection attempt, via PSTARTSQ (for the SE engine) or REMSQL (for the NET PC module).
  2. Another application already holding the single available connection, per the official guidance — both the SE engine and the NET PC module support only one connection at a time.
  3. The current application's own connection lost due to an internal error, per the official guidance, requiring the engine/module to be reloaded or the connection re-established.
Solutions / Resolution
  1. Run PSTARTSQ to load the SE engine, per the official guidance, for local database access, if it hasn't been loaded yet.
  2. Run REMSQL to load the Informix NET PC communications module, per the official guidance, for remote database access, if it hasn't been loaded yet.
  3. If already loaded, check whether another application currently holds the connection, per the official guidance, since only one is allowed at a time — close that other application's connection first.
  4. If the current application lost its own connection due to an internal error, per the official guidance, restart the engine/module and reconnect.
Examples
Loading the SE engine before connecting
> PSTARTSQ
> [application now attempts DATABASE statement]
Diagnostic Checks
  1. Confirm whether the SE engine/NET PC module has been loaded (PSTARTSQ/REMSQL).
  2. Check whether another application already holds the single available connection.
Related Errors / Related Topics

No closely related error codes are cross-referenced for -854 in this set yet.

A DOS-specific connection-setup error — load the SE engine (PSTARTSQ) or NET PC module (REMSQL) first, and confirm no other application already holds the single available connection.