We started gettting error message immediately after DB2 V11 upgrade.

Whenever IDEAL module gets some DB2 data issues its throws error message 'module DSNHDECP failed to load'.

We copied this module to DFHRPL lib of CICS region JCL then the issue resolved.

Need to understand the DSNHDECP on DFHRPL lib for V11 upgrade.

z/os, Ideal/DB2 14.0 and higher

From the 15.1 documentation: 

Performing the Post-Installation Phase

"CA Ideal™ for CA Datacom® Option for DB2 Users Only

Add the DB2 load library that contains module DSNHDECP to the DFHRPL concatenation. This module contains the DB2 default values for your site that is necessary to parse embedded SQL statements correctly during compilation.
....."

Reference:
https://docops.ca.com/ca-datacom-tools/15-1/en/installing/customization-and-postinstallation-steps-for-ca-ideal-for-ca-datacom/performing-the-post-installation-phase