Upgrade to latest release of Oracle Enterprise Manager 12c – version 12.1.0.5.0 (release).
What you can do when space in /tmp is not sufficient for upgrade agent on oem12c?
Checking the free space available at /tmp/tmp_2014_12_19_12_25_07_113 Space free : 1 GB Space required : 2 GB Actual Space Available at : /tmp/tmp_2014_12_19_12_25_07_113 is 1GB The check failed Exit Code :1 The space required for the upgrade at /tmp/tmp_2014_12_19_12_25_07_113 is not sufficient. Free the space at /tmp/tmp_2014_12_19_12_25_07_113 or provide a different staging location