The IMSLOGR files contain the save areas and checkpoint IDs for Symbolic Checkpoint (CHKP) calls. The IMSLOGR files are created the first time a CHKP call is made and added to for each subsequent CHKP call. It is read when a Symbolic Restart call (XRST) is issued to restore the program save areas. You will need to delete this file periodically as it could grow quite large. Once deleted, you cannot use XRST calls to restart from the deleted checkpoints.
These files are in the Listing directory.