The basic unit of storage for Adaptive Server is a page. Page sizes can be 2K, 4K, 8K to 16K. The server’s page size is established when you first build the source. Once the server is build the this value cannot be changed. These types of pages store database objects:
Data pages – store the data rows for a table.
Index pages – store the index rows for all levels of an index.
Large object (LOB) pages – store the data for text and image columns, and for Java off-row columns.
Adaptive Server may have to handle large volumes of data for a single query, DML operation, or command. For example, if you use a data-only-locked (DOL) table with a char(2000) column, Adaptive Server must allocate memory to perform column copying while scanning the table. Increased memory requests during the life of a query or command means a potential reduction in throughput.
The size of Adaptive Server‘s logical pages (2K, 4K, 8K, or 16K) determines the server’s space allocation. Each allocation page, object allocation map (OAM) page, data page, index page, text page, and so on are built on a logical page. For example, if the logical page size of Adaptive Server is 8K, each of these page types are 8K in size. All of these pages consume the entire size specified by the size of the logical page. OAM pages have a greater number of OAM entries for larger logical pages (for example, 8K) than for smaller pages (2K).
