HP 3000 Manuals HP 3000 Manuals
Accessing Mapped Tables IMAGE/SQL provides transparent access to TurboIMAGE/XL data.[REV BEG] However, IMAGE/SQL users should keep in mind the considerations described in this section when accessing TurboIMAGE/XL data.[REV END] Performance Considerations The following factors can affect IMAGE/SQL performance: Up-to-Date Information. When data from two or more tables is combined (joined), it is important to have accurate statistics on these tables. Use the SQL UPDATE STATISTICS statement to ensure that this information is up-to-date. Mapped table statistics should be updated immediately after the database is attached and again when the number of data entries in mapped tables has changed significantly. Refer to the ALLBASE/SQL Database Administration Guide for information about how to use this statement. Search Items in Queries. When a mapped column represents a TurboIMAGE/XL search item, IMAGE/SQL uses the search item to retrieve the data more efficiently whenever possible. (An exception: if the search item is of type P or Z, it is not used; a serial read is always done.) Because of this, using a mapped column that represents a search item in the WHERE clause of an SQL SELECT statement can improve performance in certain circumstances. Task 14, "Selecting TurboIMAGE/XL Data with SQL" in Chapter 2 describes these circumstances and gives examples of their use.