An on-demand purge provides a summary metrics report that outlines the potential impact of purge criteria. Before starting the purge, you can evaluate the number of asset versions and projects involved, and the overhead likely to be incurred. If a purge cannot execute, the summary metrics report provides detailed information on the causes of failure and points to possible remedies.
You can initiate a purge at any time through the Component Browser in the ATG Dynamo Server Admin:
/atg/epub/purge/PurgingService/
From this page, you launch an on-demand purge in the following steps:
Specify the purge cut-off date by entering the corresponding number of days in the purge cut-off field. For example:
Purge projects and unused versions of assets older than 180 days.
Click Show Metrics.
Review the data in the generated Metrics Report.
If no validation check errors occur, execute the purge by clicking Submit Purge.
The exact purge cut-off timestamp is determined by the property roundPurgeCutoffToPreviousMidnight. If set to true (default), the value supplied to the purge cut-off field is rounded to the previous midnight. If set to false, the purge cut-off timestamp is not rounded.
A Summary Metrics report is generated before the purge begins, and another one after the purge is complete. The report outlines the operation’s scope—for example, the number of projects and asset versions removed, and the number of projects and asset versions that remain. It lists results from the validation checks that the purging service uses to evaluate the versioned data to purge and, more generally, the current state of the Content Administration system. You can proceed with the purge only if all Validation Checks succeed. For example:
Cached summary metrics
By default, an on-demand purge generates a summary metric report as a background process and caches the results. This ensures that the SQL query completes execution and the resulting report can be accessed regardless of the browser state. Thus, you can navigate away from the PurgingService page before the report is complete or after viewing it; the cached report remains available for a specified period of time—by default, 24 hours. On returning to the PurgingService page, you can access the cached report via a link on the PurgingService page, and submit the purge for execution if desired. Cached report links are listed in reverse order of creation, where the most recent report is listed first.
Two properties in the component /atg/epub/purge/SummaryReportCache control caching behavior:
maximumCacheEntriesspecifies how many summary metrics reports can be cached at any one time. The default setting is5. If the number of generated reports exceeds this property, the purging service uses a least-recently-used (LRU) algorithm to determine which report to flush. If usage is equal, it flushes the oldest report. To disable caching, set this property to0.maximumEntryLifetimespecifies in milliseconds how long a report can remain cached before it is invalidated. The default setting is86400000(24 hours).
After a purge executes, all summary metrics report caches are flushed.
Purging unused target branches
Any purge, regardless of the cut-off date, removes all unused target branches and their assets from the versioning system. Thus, you can initiate a purge that removes only those branches by setting an unrealistically high cut-off date—for example, 14,000.
