Database Reference
In-Depth Information
Having said that, you do need to be aware of some other areas that you can manage from within SQL*Plus for
the repository, particularly around space consumption and performance considerations. In this section, you'll learn
about the following:
•
Data retention
•
Queue management
•
Optimizer statistics
•
Repository views
Data Retention
Enterprise Manager gathers a lot of data. This data is processed and aggregated in the following lifecycle by default:
•
Raw metric data, which is uploaded by the management agent according to the collection
policy you define, is kept for 7 days.
•
After 7 days, only hourly summaries (maximum, minimum, and average values for metrics)
are kept.
•
These are kept by default for 31 days, after which only daily summaries are kept.
•
Finally, the daily summaries are kept for 12 months.
You likely will want to review these policies. In particular, a common task carried out by target administrators
is to compare performance with the previous business cycle. It's therefore likely that you would want raw metrics
available for longer than 7 days in order to drill down into more-granular data. Similarly, you might want to keep
hourly data for more than a month so that you can, for example, compare month-end data between months. Finally,
many organizations choose to keep daily data for many years.
■
enterprise Manager uses partitioning in the repository database to maintain metric and other data. this
would normally be an added feature as far as licensing is concerned, but provided you use only the partitioning option for
enterprise Manager base tables, you do not need to pay extra. please do
not
relink oracle without partitioning, as i had
one customer do who was concerned about extra licensing costs. you will seriously break the repository if you do!
Caution
Enterprise Manager archives old data by dropping aged-out partitions for the metric tables. The retention policy
can therefore be set by modifying the number of partitions to keep. Enterprise Manager provides a stored procedure
to perform exactly this task. Listing 3-1 implements a retention policy of 10 days for detail data, 40 days for hourly
data, and 3 years for daily data.
Listing 3-1.
Modifying EM Retention Policies
BEGIN
sysman.gc_interval_partition_mgr.set_retention('SYSMAN','EM_METRIC_VALUES',10);
sysman.gc_interval_partition_mgr.set_retention('SYSMAN','EM_METRIC_VALUES_HOURLY',40);
sysman.gc_interval_partition_mgr.set_retention('SYSMAN','EM_METRIC_VALUES_DAILY',36);
END;
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