DL/I I/O errors and recovery

The way IMS handles DL/I I/O errors allows you to delay database recovery until it is convenient.

If the errors do not recur or can be corrected automatically, recovery might even be unnecessary. IMS maintains data integrity by reconstructing information about I/O errors on later warm or emergency restarts.

When an I/O error occurs, IMS issues message DFS0451I and creates an extended error queue element (EEQE). When IMS successfully forward recovers a DBDS with an EEQE, DBRC updates the appropriate entries in the RECON data set, and IMS removes the EEQE.

You can use the /DISPLAY DB command with the BKERR keyword to display information about the outstanding EEQEs associated with a database.