Checkpoint determination

IMS DEDB Fast Recovery determines the recovery start checkpoint from the checkpoint ID table that is created during the OLDS processing.

If no DL/I database is defined for the IMS to be recovered, or if LCHKPT=Y is specified, IMS DEDB Fast Recovery uses the Fast Path checkpoint identifier (BCPFCKID) as the recovery start checkpoint. If DL/I databases are defined for the IMS to be recovered and LCHKPT=N is specified, IMS DEDB Fast Recovery uses the oldest of the following identifiers as the recovery start checkpoint:

BMP checkpoint identifier (BCPBMPID)
LCRE checkpoint identifier (BCPLCKID)
Fast Path checkpoint identifier (BCPFCKID)

If DBRC=Y is specified in the EXEC parameter of IMS DEDB Fast Recovery, IMS DEDB Fast Recovery determines the log data set containing the recovery start checkpoint by using the OLDS/SLDS information in the RECON data set. If DBRC=N,AUTO=Y, the log data set is determined from the OLDS entry table (DSET) if it was created during the OLDS processing. If DBRC=N,AUTO=N, or if a DSET has not been created, or if SLDS contains the checkpoint, a WTOR message (DFR3110A) is issued. The operator must then reply with the DD name of the OLDS or SLDS that contains the checkpoint indicated by the DFR3301I message.

IMS DEDB Fast Recovery opens the selected OLDS or SLDS if the DD statement for the data set is specified in the JCL. If there is no DD statement, the data set is allocated dynamically and opened.

Note: For dynamic allocation, the user must register the request block in the IMS program library with the DFSMDA macro. See IMS System Definition for details about the DFSMDA macro.

IMS DEDB Fast Recovery then reads the X'4001' log record of the recovery start checkpoint (checkpoint start log record) and checks if the IMS identifier in the log record (or the RSE identifier in the XRF complex) matches the identifier specified by the EXEC parameter.