A storage policy provides mapping to specific physical storage area(s) and is used to specify where content is stored for a given class or object with content (for example, a document). Content Engine supports the mapping of storage policies to one or more storage objects; therefore, each storage policy can have one or multiple storage areas as its assigned content storage target. This concept is known as "farming".
A storage area "farm" is a group of storage areas (a subset of the available storage areas) acting as a single logical target for content storage. With farming, Content Engine provides load-balancing capabilities for content storage by transparently spreading the content elements across multiple storage areas. The number of storage areas that can be added to a farm is limited only by the length of the concatenated storage location string value that will fit into the Storage Locations property.
Therefore, the storage policy functions as both the mechanism for defining the membership of a storage area farm, and also the means for assigning documents to that farm.
You can assign storage areas to a storage policy by either: 1) select storage areas from a list of available storage locations, or 2) create a filter expression to explicitly assign storage areas based on a customized string expression. If you choose to select storage areas from a list, Content Engine translates that list into a filter expression.
The storage policy filter expression is a string valued property that behaves in the same manner as a “WHERE” clause of a SQL SELECT statement. You can edit the filter expression directly to select storage areas that meet specific user requirements.
This filter expression always implicitly includes “AND AreaStatus=Open”. Note that it is not a requirement that the storage areas that satisfy the criteria are all the same type. The filter criteria, however, are restricted to the queryable properties of the StorageArea class and subclasses; thus, the statistical properties (displayed in red in the storage area properties grid) are excluded from consideration.
Filter Expression Value | Result |
(1>0) |
returns all Storage Areas |
IsClass(Source,DatabaseStorageArea) |
returns all Database Storage Areas |
IsClass(Source,FixedStorageArea) |
returns all Fixed Storage Areas |
IsClass(Source,FileStorageArea) |
returns all File Storage Areas |
Id IN ({A178B949-9B20-42EA-B58E-03175AD3879C}) |
returns the Storage Area with ID = A178B949-9B20-42EA-B58E-03175AD3879C |
Id IN ( {GUID1}, {GUID2} ) |
Returns a “farm” of multiple storage areas with IDs = GUID1 and GUID2 |
IsClass(Area,CenteraStorageArea) AND RetentionPeriod > 60 |
Returns Centera storage with at least 5 years (60 months) retention |
When an object store is created, a default database storage area is created in the “open” state and is the default storage area for those classes that can store content. A default storage policy is also created, with no filter expression – so all “open” storage areas are available for content storage.
Enterprise Manager provides a wizard to guide you through the process of creating a new storage policy and assigning to it a list of storage areas. The available storage policies for a given object store are then displayed under the Storage Policies node.
Once a storage policy is created, it can be assigned as the default storage policy for class objects, thus giving the class objects a pointer to a physical storage location for storing content.
NOTE