Chapter 10. Migration and expiring data and indexes 223
Typically, this methodology is employed under the following circumstances:
/SM590000Most of the data access occurs during the initial period. After that period, the data is 
infrequently accessed, if ever. So, after this initial period, the data is migrated to the 
storage manager.
/SM590000A performance advantage is possible if you retrieve the data from cache versus if you 
retrieve the data from the storage manager. The performance advantage for cache can 
occur if the storage manager is on a device that is separate from the Content Manager 
OnDemand object server, or if the storage manager is local but the storage device is 
relatively slow, such as tape or an optical disk.
Migrating data from cache
This function, which can be accessed by clicking Advanced on the Storage Manager tab of 
the Application Group window, determines how long the data is kept in cache before it is 
migrated to archive storage (on a potentially slower archive storage device). 
The data needs to be kept on a high-performance storage device for the period during which 
it is retrieved frequently. The storage set must support the type of media that is required to 
hold reports that are stored in the application group. For example, if you must maintain 
reports in cache storage for 90 days and in archive storage for seven years, the storage set 
must identify a storage node (or migration policy) that causes ASM to maintain the data for 
seven years, and you must select Cache Data for __ Days and enter 90 in its field.
From a user’s perspective, no procedural difference exists in retrieving the data from either 
cache or archive storage. The only user-perceivable difference is the response time. Various 
archive storage mechanisms provide different performance profiles. For example, when you 
use OAM and the data is stored in DB2 tables on disk, the response time is as fast as the 
cache response time. The main difference in response time is based on the type of disk that is 
used by either method. Conversely, if the OAM data is stored on optical disks or tape, the 
response time is increased dramatically. If you use a network-attached Tivoli Storage 
Manager server, the retrieval rates (throughput and response times) are governed by the 
Tivoli Storage Manager device and the TCP/IP connection to that device.
Typically in a z/OS environment, data is not stored in cache. Content Manager OnDemand for 
z/OS customers typically use OAM as their storage manager. OAM supports storing the data 
directly in DB2 where the storing and retrieval rates are exceptionally fast, which eliminates 
the need to maintain and monitor cache file systems in the z/OS file system (zFS) or the 
hierarchical file system (HFS).
Scenario 3: Storage manager only, then expiration
The storage object is stored directly to the storage manager. Typically, this methodology is 
employed under the following circumstances:
/SM590000The performance of the storage manager equals the performance of the local file system, 
which implies that the storage manager stores data to a relatively fast device, such as 
local disk.
/SM590000Hierarchical storage management is beneficial. An example is z/OS systems where 
storing directly to OAM is the most popular solution.
If you do not need to maintain reports in cache storage, select a storage set that identifies a 
storage node (or migration policy) that is maintained by ASM and set Cache Data to No. 
Content Manager OnDemand automatically sets Migrate Data from Cache to When Data is 
Loaded.