The metrics gathered for each collection interval are stored in their own database tables.

At the end of an interval, one of two things can occur.

If the next interval is disabled, the data in the table that is older than the interval duration is purged.

If the next interval is enabled, the data is aggregated into groups and is rolled up to the database table of the subsequent collection interval. For example, the day interval has a 5 minute collection frequency, and the week interval has a 30 minute collection frequency. When the day interval completes, it aggregates the 5 minute queries into groups of six (equaling 30 minutes) and rolls the 30-minute data block to the week interval database table. The day-old data is then purged from the database to make room for new queries.

You control how long statistical data is stored in the vCenter Server database by enabling or disabling a collection interval. When you disable a collection interval, all subsequent intervals are automatically disabled. For example, when you disable the week interval, the month and year intervals are also disabled. Data is purged at the end of the day interval cycle because no rollups can occur. The oldest data is purged first.

Note

You must manually enable each collection interval to use it again. Also, you can only enable a collection interval if all previous statistics intervals are enabled. For example, to enable the month interval, the day and week intervals must be enabled.

By default, statistics are stored in the vCenter Server database for one year. You can increase this to three years. To save statistical data for longer than three years, archive it outside of the vCenter Server database.