Storage requirements overview

To estimate storage requirements for a Content Manager OnDemand system, you must understand and document user requirements for storing and accessing data.

Reports and other data provides information that can help you gather user requirements.

Before you turn requirements into a storage subsystem to support your system, you must also review the various operational and performance issues. For example, Content Manager OnDemand supports up to 128 index fields for each report. However, users typically do not need many indexes to locate a specific version of a report or a document within a report. The number of index fields that you define has a direct impact on the amount of disk space that you need for your database.

In addition, the more indexes that you define for a report, the more time is required to load the report into the system. You must work with users and understand their data retrieval requirements. Define only the number of index fields that they need. You might have to balance user requirements with disk space, the amount of time required to load a report, and other performance issues.

Maintaining a copy of reports in cache storage can significantly impact the amount of disk storage that you need on your system. Most customers store the latest versions or most frequently accessed reports in cache storage. You should review how users search for and retrieve information from the reports that you plan to store in Content Manager OnDemand. For example, if most retrievals occur in the first 90 days after a report is generated, then you probably want to store the report in cache storage for at least that length of time. You should choose a time to cache each report that meets the requirements of your users and also makes the best use of available cache storage space.

You need several components to measure to determine the amount of disk, optical, and tape storage required to support a Content Manager OnDemand system. For example, the following components of the system require disk storage:

Storage space for application programs and system software, including the base operating system, the Content Manager OnDemand server software, and the database manager and optional components such as the archive storage manager and the server print manager.
Storage space for configuration files and control files.
Storage space for the Content Manager OnDemand system logging facility.
Temporary storage space for reports received from other systems. In general, you should plan for enough disk space to hold either the largest single report that you will be loading on the system or the total of several reports that might be staged for loading at the same time, whichever requires the most storage space. In many organizations, most versions of a report are similar in size. However, there might be times when a report is much larger than average. For example, a report generated at the end of the month or the end of the quarter might greatly exceed the average report size.
Temporary storage space for indexing a report on the Content Manager OnDemand server.
Temporary storage space for loading a report on the Content Manager OnDemand server.
Cache storage. This can be zero, for reports that do not require cache storage. However, a very large amount of disk space might be required for reports that must remain in cache storage for several months or longer.
Content Manager OnDemand compresses report data before storing it on storage volumes. The compression ratio can have a significant impact on the amount of disk space that you need to store a report in cache storage. Content Manager OnDemand can achieve up to 30:1 compression on line data reports. However, for reports that contain AFP™ data or image data that is already compressed, the compression achieved will be much lower.
Storage space for the database, which includes Content Manager OnDemand system tables (control information and objects that you define to Content Manager OnDemand) and application group tables (index data extracted from reports). The amount of database space that you should plan for a report is a factor of the number of items contained in the report, the number of index fields that you define for the report, the number of versions of a report (or the frequency with which you load a report on the system), and how long you need to maintain a report on the system.
For reports that contain sorted transaction data, Content Manager OnDemand can divide the report into groups of a fixed number of pages and create one index row for each group of pages. (For sorted transaction data, the examples and calculations that follow assume that Content Manager OnDemand will create one indexed item for each group of 100 pages in a report. The number of pages in a group is a parameter that you can configure when you index a report with ACIF. The Content Manager OnDemand Indexing Reference provides move information. For reports that contain logical items, such as statements, and policies, Content Manager OnDemand can create one index row for each logical item in the report. Typically the database space required for indexing sorted transaction data is much less than the database space required for indexing reports that contain logical items. Also, index fields provide fast lookup, but require a significant amount of database space.
Storage space for database log files. You should plan for disk space for active or primary log files and for log files that are not active but might still be needed for recovery (sometimes known as archived log files).
Storage space for the database and logs used by the archive storage manager.
Temporary storage space for server print.
Temporary storage space for importing migrated indexes from archive media to the database.

The following components of the system require archive storage (optionally VSAM files or OAM objects):

Reports that you plan to store on archive media.
Back up copies of reports stored on archive media. (For critical applications, you might require that the system maintain two or more copies of a report on archive media.)

When you calculate archive storage requirements, you should also determine the number of storage volumes and libraries that you need to support the data that will be stored on your system. Optical libraries are capable of holding a large amount of data, with the storage capacity usually expressed in amounts of uncompressed data.

Depending on the compression ratio achieved for your reports, an optical library might be able to hold more than the stated amount. For example, if Content Manager OnDemand can achieve a 6:1 compression ratio on the reports that will be stored in an IBM® 3995 optical library, the library can hold multiple terabytes of report data, depending on hardware configuration.

You can replace full optical storage volumes as needed, if the availability requirements of your system allow you to do so. For example, you might decide to remove full storage volumes from a library one year after the last time that Content Manager OnDemand wrote report data to the storage volume. You could replace the full storage volumes with newly initialized storage volumes to hold the latest reports stored on the system. That way, the latest versions of a report are always available in the library. However, if you need to keep many years of report data online in the library or you store massive amounts of data in your application groups, then you might need to plan on having several optical libraries for your system.