Error 27001, Unable to connect via tcp network connections

Problem(Abstract)

This article describes three common causes for listener-thread: err = -27001: Read error occurred during connection attempt errors.

Symptom

This error appears in the IBM® Informix® Dynamic Server (IDS) message log file (ONCONFIG configuration file parameter MSGPATH) and users are not able to connect to the database server.:

listener-thread: err = -27001: Read error occurred during connection attempt.

Resolving the problem

Common causes and solutions for the error are:

1. The connectivity files in the /INFORMIXTMP directory are not removed.

The files are in the form of : VP.server_name.0100a


server_name
Database server name as was set in INFORMIXSERVER environment variable and associated with the tcp connections.

Solution:

Stop the database server, remove the files from the /INFORMIXTMP directory, and start the database server.

2. The onCONFIG file settings for the NETTYPE parameter are not correct. This error is widely seen involving tcp network connections when the VP class in the NETTYPE setting is set for CPU vp.

Solution:

As a work around Change the vp class setting for the NETTYPE configuration parameter from CPU to NET.

Factors outside of Informix that can cause 27001

3. An operating system resource limit was reached. Kernel parameters settings require changes.

Solution:

Check and possibly increase settings for the following kernel parameters or parameters equivalent to them depending on Unix platform:

• NOFILES
• SEMMNU
• NFILES
• MAXFILES
• MAXFILE_LIM

4. Network problem. Perhaps the network is busy or packets are being lost. Monitor network and alleviate the problem.

5. Hardware involved in the system ( network card, cables, router, and so on ) is intermittently failing and causing the error.

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