automatically. Indexes on user-defined item attributes are not generated automatically. You must define them manually. For the attributes that are frequently used for regular searches, define indexes on these attributes to improve response time and reduce Library Server resource usage for queries over these attributes. The system administration client provides a point-and-click interface to define indexes. You can choose one or a combination of attributes to create each index and you can specify the order of the index, either ascending or descending. Use combinations of attributes to create the index where users typically use that combination of attribute values to find items in the item type. Content Manager cannot anticipate the way your application will choose to search for the data. Application queries are embedded in the compiled programs as Dynamic SQL, which enables the system to calculate the access path at run time. This means that the database optimizer calculates the best access path to the data for your queries when they are run. The database then immediately starts using your indexes for queries after the indexes are created, assuming that the optimizer chooses to use them. The optimizer might decide that the indexes do not help resolving the queries because they are on the wrong columns or because the optimizer is working with outdated statistical information about the table. It is always a good idea to run runstats soon after you create an index so that the optimizer has the best information. If you do run runstats, it is also a good idea to rebind the database packages as well. The optimizer might be able to use the new index to improve access speed for other SQL and might improve other access paths based on the new statistical information. Unless there is a major performance problem affecting most users at the time, it is best to create indexes, run runstats, and rebind at times of low user activity. These utilities can have a negative impact on server performance while they are running. See 8.2.5, “Create attribute indexes” on page 177 for details about creating indexes for attributes. See 8.3.3, “Keeping database statistics and execution plans up to date through runstats/rebind” on page 183 for more about runstats and rebind.
Multiple item types Many Content Manager applications tend to work actively on an item while it is relatively new to the system. At some point, that work completes and the item is archived. For these types of applications, it can be a performance advantage to separate the active documents into a separate item type from those that have already been dealt with (archived). Sooner or later the archived documents will out-number the active documents, and all being well, the number of active documents should plateau or at least have relatively slow growth. The number of
Chapter 5. Designing and configuring for performance
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