Enterprise Manager Cloud Control is not currently available ! Como resolver?

Ao tentar logar no Oracle Cloud Control o seguinte erro era apresentado: Enterprise Manager Cloud Control is not currently available. The EMGC_OMS server where Cloud Control runs, or some other component, might be down. Retry

Ao que indica, um dos componentes estavam parados: database, listenet ou middleware. Iniciei a checagem pelo banco de dados, depois listener e por fim o middleware do Oracle Cloud Control:

Banco de dados: o banco de dados estava down, porém mesmo após subi-lo o Oracle Cloud Control continuava fora:

[oracle@server01 ~]$ sqlplus / as sysdba
SQL*Plus: Release 12.1.0.2.0 Production on Tue Aug 6 11:28:24 2019
Copyright (c) 1982, 2014, Oracle. All rights reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area 1.3388E+10 bytes
Fixed Size 2939512 bytes
Variable Size 5469373832 bytes
Database Buffers 7885291520 bytes
Redo Buffers 30613504 bytes
Database mounted.
Database opened.

Listener: O listener também estava parado e após iniciá-lo o Oracle Cloud Control continuava fora:

[oracle@server01 bin]$ cd $ORACLE_HOME/bin
[oracle@server01 bin]$ ./lsnrctl start
LSNRCTL for Linux: Version 12.1.0.2.0 – Production on 06-AUG-2019 11:31:05
Copyright (c) 1991, 2014, Oracle. All rights reserved.

Starting /u01/app/oracle/product/12.1.0.2/db_1/bin/tnslsnr: please wait…

TNSLSNR for Linux: Version 12.1.0.2.0 – Production
System parameter file is /u01/app/oracle/product/12.1.0.2/db_1/network/admin/listener.ora
Log messages written to /u01/app/oracle/diag/tnslsnr/server01/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server01)(PORT=1521)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=server01)(PORT=1521)))
STATUS of the LISTENER
————————
Alias LISTENER
Version TNSLSNR for Linux: Version 12.1.0.2.0 – Production
Start Date 06-AUG-2019 11:31:05
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/oracle/product/12.1.0.2/db_1/network/admin/listener.ora
Listener Log File /u01/app/oracle/diag/tnslsnr/server01/listener/alert/log.xml
Listening Endpoints Summary…
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=server01)(PORT=1521)))
(DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
The listener supports no services
The command completed successfully

Middleware: Restou subir o Middleware para verificar se o serviço estaria disponível. Ao checar o status do serviço, verificamos que o OMS, JVMD Engine e o BI Publisher Server estavam parados:

[oracle@server01 ~]$ cd /u01/app/oracle/middleware/bin
[oracle@server01 bin]$ ./emctl status oms
Oracle Enterprise Manager Cloud Control 13c Release 1
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
WebTier is Up
Oracle Management Server is Down
JVMD Engine is Down
BI Publisher Server is Down

Comando utilizado para iniciar o serviço:

[oracle@server01 bin]$ ./emctl start oms
Oracle Enterprise Manager Cloud Control 13c Release 1
Copyright (c) 1996, 2015 Oracle Corporation. All rights reserved.
Starting Oracle Management Server…
WebTier Successfully Started
Oracle Management Server Successfully Started
Oracle Management Server is Up
JVMD Engine is Up
Starting BI Publisher Server …
BI Publisher Server Successfully Started
BI Publisher Server is Up

Após o start do serviço, o Cloud Control voltou a funcionar como estava antes: