Today, we had the chance to attend interesting sessions under a perfect sunny Californian weather :-). The first one was about best practices for an upgrade to Oracle Enterprise Manager 12c. The session described the real case of a US company with a huge infrastructure and hundreds of databases monitored by Grid Control 11g and 800 agents. They wanted to migrate to Oracle Enterprise Manager Cloud 12c and studied the different ways to realize the migration.

OWW-AvionThey choose to migrate to Oracle Enterprise 12c mainly because of these new features:

  • Compliance
  • Metric extensions and template collections
  • Agent control from the console
  • Integrated configuration tools
  • Automatic applying metrics

There are in fact two approaches outside of a fresh install:

The first possibility is a system upgrade:

  • Start with 10.2 or 11.1 system
  • Apply pre-upgrade patch
  • Deploy agents 12c from pre-upgrade console
  • Run health check on 12c agents
  • Shutdown 10.x or 11.x agents
  • Start agent 12c
  • Backup repository
  • Shutdown OMS 10g or 11g
  • Install OMS 12c and start the OMS 12c (this is the downtime period)

The second possibility is a systems approach:

  • Apply pre-upgrade patch
  • Deploy 12c agents from pre-upgrade console
  • Backup repository
  • Deploy OMS 12c
  • Upgrade backed-up repository to 12c
  • Start OMS 12c
  • Switchover 10g or 11g agents and activate 12c agents

The main question is: Do I choose a fresh install or an upgrade?

The fresh install has the following inconvenients:

  • Loss of historical data
  • Necessity to push agents on all targets hosts where old agents exist, necessity to open new ports
  • Perform post install tasks: setup software library, create users and new policies
  • Need of new hardware for em12c OMS

The system upgrade has the following advantages:

  • All historical data is kept
  • Necessity to upgrade all agents, no need to open new ports
  • Only a few post install tasks such as configuring the software library

So the decision has been taken to upgrade to Oracle Enterprise Manager 12c using the second approach.

These are the major steps followed by the DBA:

  • Get the right software and patch from OTN
  • Deploy 12c agents
  • Repository backup
  • OMS and repository upgrade
  • Agent health check and switchover
  • Post upgrade verification

The case was very interesting because of the huge volume of the repository. For example, the upgrade of the repository lasted about 26 hours for a volume of 800 GB, and they did not have any repository upgrade failure also because the memory parameters of the repository database were well configured.

They only had problems with the agent health check and switchover because the 11g agents were not secured, and the OMS 12c is secured by default, so the 12c agents were deployed but could not communicate with the OMS 12c.

For your information, one DBA realized this wonderful but long job without any downtime:

  • Pre-upgrade console , read documentation, get binaries from OTN, agents issues: 2 weeks
  • Upgrade agents: 3 weeks
  • Backup and restore repository: 2 days
  • OMS install and repository upgrade: 2 days
  • Verify post upgrade tasks (target data migration, deferred data migration): 7 days
  • Agents switchover, agents health check: 4 weeks

At the end the total migration time was about 11 weeks, but with no downtime, Grid 11g was available to users the entire time and the overall operation was a success.