Set the login info, otherwise you will give session expired error.
./emcli setup -url=https://source_hostname:7799/em -username=sysman
./emcli export_report -title="Database Size" -owner="SYSMAN" -output_file="db_size.xml" Report "Database Size", owned by "SYSMAN", has been exported from the repository. Exported reports may not contain all information from original report. Repository specific information such as targets, administrator access, and schedules are not exported. Imported reports should be edited after import to supply all necessary report parameters.
In target
./emcli setup -url=https://target_hostname:7799/em -username=sysman
./emcli import_report -files="db_size.xml" File "db_size.xml" has been imported into the repository. Imported reports should be edited after import to supply all necessary report parameters.