DB Connection not set (SAP HANA or TREX)

What causes this issue?

To enable SAP HANA, TREX/BWA and SAP NetWeaver to communicate with one
another, create a connection between them.
If you use SAP HANA you have to create a database connection from SAP
NetWeaver to SAP HANA.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Specify a DB connection to SAP HANA or TREX/BWA destination. Run
transaction ESH_IMG and navigate into the common settings.
Have a look for the Enterprise Search specific task list
SAP_ESH_INITIAL_SETUP_WRK_CLIENT and check if the client is prepared for
Enterprise Search. The transaction for processing task lists is STC01.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.