A CEEDLLF DLL failure control block is populated with further DLL error diagnostics. If the _EDC_DLL_DIAG environment variable is not set to QUIET, the error message is sent to the Language Environment message file. Other DLL diagnostic options, such as issuing ctrace(), signaling a condition, and the ability to turn off _EDC_DLL_DIAG diagnostics, are available through the _EDC_DLL_DIAG environment variable.