The Central Inventory contains information relating to all Oracle products installed on a host. It contains an inventory file and a logs subfolder that contains OUI and OPatch logs.
Windows: Central Inventory is in System Drive/program files/Oracle/inventory
Linux: Central Inventory location is specified in the oraInst.loc file, which is in the /etc folder.
Central Inventory log files are saved in this format: ActionTimestamp.log. For example, this log is recorded for an AttachHome operation performed on May 17, 2010, at 6.45AM: AttachHome2010-05-17_06-45-00AM.log.