How to Get EM 12c Agent Software Using Self Update in Offline Mode?

1. Ensure EM 12c Cloud Control is set to the offline mode
From the "Setup" menu, choose "Provisioning and Patching" -> "Offline Patching", then change the setting for "Connection" to "Offline". Optionally you can upload the catalog to keep EM up-to-date with patch recommendations in this screen too.

2. Acquiring Management Agent software in the offline mode
From the "Setup" menu, choose "Extensibility" -> "Self Update".
Select the entity type "Agent Software" and choose one.
Click "Download", a message box is displayed with a URL and instructions.

Download the file from a computer with Internet connection and copy the file to the computer where your EM installation resides.

3. Import Management Agent software into OMS using emcli
$OMS_HOME/bin/emcli login -username=sysman

$OMS_HOME/bin/emcli import_update -omslocal -file=/home/oracle/Desktop/p14570372_112000_Generic.zip

Refresh "Self Update" page, corresponding Agent software status will be changed to "Downloaded".

References:
MOS Note ID 1369575.1