Emergency starting IMS

After IMS terminates without a controlled shutdown, you must perform an emergency restart. The one exception is if an emergency restart fails; in this case, you must perform a cold start with the /ERESTART COLDSYS command.

For an emergency restart, IMS restarts from the point of failure. Before restarting IMS, the MTO must know whether system data sets must be reallocated and reformatted during restart. The following table shows symptoms (a message or abend number) that indicate whether a system data set needs reallocation and reformatting.

Table 1. Symptoms indicating system data set reallocation is needed . Key: N/A=Not Applicable
System data set Write error Read error Data set full Open error
WADS DFS0414I DFS739I N/A DFS3256I
Message queue U0759 U0759 U0758 DFS986A
Restart data set (RDS) DFS3127I U0970 N/A U0970
MSDB checkpoint or MSDB dump DFS2718I, DFS2722I N/A N/A DFS2681I, DFS2713I, DFS2714I

The following situations cause the abends shown in the previous table.

U0758
An IMS internally generated /CHECKPOINT DUMPQ command failed after messages DFS206I, DFS207I, or DFS208I because one of the message queue data sets is full.
U0759
An error occurred while attempting to read or write the message queue data sets.
U0970
The restart data set (RDS) or checkpoint table was not initialized, or restart was unable to open the input log.

If the WADS has not previously been formatted, you should format it by specifying the FORMAT WADS keywords on the /ERESTART command. If you want to reformat any of the message queue data sets, specify the BLDQ keyword. If no checkpoint specifying either DUMPQ or SNAPQ has been taken since the last cold start, specify CHECKPOINT 0 on the /ERESTART command.

During Extended Specified Task Abnormal Exit (ESTAE) routine processing, IMS issues message DFS0617I if the RDS buffers have been purged and the RDS has been successfully closed. However, if you do not receive this message, you do not necessarily have to reformat or reallocate the RDS.

Requirement: You should reformat the RDS if you receive message DFS3127I or abend U0970, either of which indicate a read or write problem with the RDS. However, if the error has nothing to do with the RDS, you should not reformat the RDS. If errors occur on both MSDB checkpoint data sets:

Procedure

  1. Issue the /ERESTART command.
  2. Issue the /DBDUMP DB or UPDATE DB STOP(UPDATES) command for the MSDBs.
  3. Shut down the system (in a controlled way).
  4. Run the MSDB Dump Recovery utility.
  5. Restart the system using an /NRESTART command, including the MSDBLOAD keyword so that IMS can reload the MSDBs.