Interactions among policy settings
Time-based and version-based policy settings interact when used together in a management class for a policy. The frequency of client backups also affects the backup versions that are stored for a client.
- You set Keep Extra Backups to 30 days. You set Backups to No limit so that the policy does not limit the number of versions. After 30 days, the server might have 60 backup versions of the file, if the file changes between each of the two daily backup operations. The client can choose to restore any of the 60 versions from the past 30 days.
- You set Keep Extra Backups to No limit, and set Backups to 30 versions. If the file changes between each of the two daily backup operations, the server has 30 backup versions after 15 days. After 30 days, the server still has only 30 backup versions because of the limit on the number of versions. If the file continues to change between each of the two daily backup operations, the backup versions might be from as few as the last 15 days. The client can choose to restore one of the 30 versions, which might be no older than 15 days.
The examples show that if backup versions must be available for a specific number of days, the simplest way to implement that requirement is to use a time-based policy. Set Keep Extra Backups to the specific number of days and set Backups to No limit.
The effect of the No limit value in the policy settings varies according to what other policy controls are set:
- Keep Extra Backups
If you specify No limit, inactive backup versions are deleted based on the Backups or Deleted Backups settings.
To enable client nodes to restore files to a specific point in time, set the Backups or Deleted Backups to No limit. Set Keep Extra Backups to the number of days that you expect clients might need versions of files available for possible point-in-time restoration. For example, to enable clients to restore files from a point in time 60 days in the past, set Keep Extra Backups to 60.
- Keep Deleted Backups
If you specify No limit, the last version is retained forever unless a user or an administrator deletes the file from server storage.
- Backups
Setting the value to No limit can require increased storage, but that value might be necessary to specify for some situations. For example, to enable client nodes to restore files to a specific point in time, set the value for Backups to No limit. By not setting a limit on versions, you ensure that the server retains versions according to the Keep Extra Backups setting.
- Deleted Backups
Setting the value to No limit can require increased storage, but that value might be necessary to specify for some situations. For example, set the value for Deleted Backups to No limit to enable clients to restore files to a specific point in time. By not setting a limit on versions, you ensure that the server retains versions according to the Keep Extra Backups setting.
Cross-reference for Operations Center fields and server command parameters
The following table shows the Operations Center fields with the equivalent parameter to use with the DEFINE COPYGROUP TYPE=BACKUP command.| Field name in Operations Center views | Parameter to use with the DEFINE COPYGROUP TYPE=BACKUP command |
|---|---|
| Keep Extra Backups | RETEXTRA |
| Keep Deleted Backups | RETONLY |
| Backups | VEREXISTS |
| Deleted Backups | VERDELETED |