Oracle Database 12c: EM Express Database Administration
Oracle Enterprise Manager Database Express, also referred to as EM Express, is a database management tool that focuses primarily on performance management and monitoring. However, it does include basic administration functions to assist the database administrator.
When users first log into EM Express, they see the home page which displays information about the database, as well as performance data, such as resource usage, average active sessions, and monitored SQL statements.
Database Administration Functions
The three main categories of administrative tasks are:
Configuration Storage Security
The four main features available in the Configuration menu are Initialization Parameters, Memory Configuration, Database Feature Usage and Database Properties.
Database Administrators can view and set initialization parameters for one or more instances of the database. They can also determine how memory has been configured, and in particular, the amount of memory allocated to the SGA and PGA, the top processes consuming memory, and whether or not any of the automatic memory management features are in use. In addition, memory advisor data is also displayed on the page. To see an example of the Memory page, click here.
As part of Storage administration, DBAs can manage redo logs, archive logs, and tablespaces (view space consumption, create and/or alter tablespaces). In addition, DBAs are also given some visibility into the control file contents. DBAs can also view the Undo Advisor, as well as undo statistics, such as the undo generation rate and undo space usage. To see an example of the Undo Page, click here.
DBAs can use the features available in the Security menu to manage users, roles and profiles by creating, altering or granting and revoking privileges from them.
The advisor data visible at the top right panel of the Memory page is dependent on the memory configuration settings that are in use.
If Automatic Memory Management is used, then only the Memory Advisor is displayed on the page.
If Automatic Shared Memory Management is used, then the SGA Advisor, along with the PGA Advisor is displayed.
If Manual Shared Memory Management is used, then the Buffer Cache Advisor, along with the PGA Advisor is displayed
I'm trying to perform a task that I used to do in DB Control. Where is it in EM Express?
EM Express is not a direct replacement for DB Control. As explained in the Architecture section, EM Express is built inside the database server and there are limitations as to what it can do. EM Express is also focused on providing performance management and monitoring functionality, and is not meant to be an all around database administration tool.
Why do I see a "Warning" icon on the Memory Page?
The warning icon is displayed if the memory configuration is different across the instances in your RAC cluster. For example, this may be displayed if one instance uses Automatic Memory Management, while the other instance uses Manual Shared Memory Management.
In the Memory Page, why are the sizes in the Configuration region different from the Allocation region?
The configuration section shows the parameters that have been specified by the user, while the allocation section shows the amount of memory that has been allocated. For example, if the system is using sga_target, the user can still specify minimum sizes for the different pools, and these sizes will be displayed in the Configuration section. However, the allocation section will show what the system has allocated for the pools.
For an example, click here. shared_pool_size=512M in the Configuration section, yet the Allocation breakdown shows 1G has been allocated.
In the Memory Page, why does sga_target in the Configuration region show a different value from the Current Setting in the SGA Advisor region
This can happen on RAC. The Configuration region shows the aggregate across all instances in the RAC target. However, when showing the SGA Advisor data, if the sga_target is the same on all instances, it shows the advisor data based on the sga_target setting of the instances, with the estimated percentage of time taking into account the time saved over all instances.
For an example of a 2-node RAC environment with sga_target=2000M on each node, click here. The page shows sga_target=3.9G, but the Current Setting in SGA Advisor shows 2G.
I'm on a RAC system, and the Home Page shows "Host CPU". Which host is it showing?
This shows cluster CPU utilization. If you have a symmetric cluster, this is the average of CPU utilization across all the nodes. If you have an asymmetric cluster, then this shows the utilization over the entire cluster, e.g. sum of CPU used / sum of available CPU.
Similarly, the other charts in the Resources region, such as Active Sessions and Memory, also show aggregated values over the entire cluster. For an example, click here.
To see the details per instance, click on the RAC link in the Status region, from the live UI.