You set a page size for the IQ store with the IQ PAGE SIZE option. This option determines memory and disk use. The IQ PAGE SIZE must be a power of 2, from 65536 to 524288 bytes. The IQ page size is the same for all dbspaces in the IQ store.
To obtain the best performance, Sybase recommends the following minimum IQ page sizes:
64KB (IQ PAGE SIZE 65536) for databases whose largest table contains up to 1 billion rows, or a total size less than 8TB. This is the absolute minimum for a new database. On 32-bit platforms, a 64KB IQ page size gives the best performance.
128KB (IQ PAGE SIZE 131072) for databases on a 64-bit platform whose largest table contains more than 1 billion rows and fewer than 4 billion rows, or may grow to a total size of 8TB or greater. 128KB is the default IQ page size.
256KB (IQ PAGE SIZE 262144) for databases on a 64-bit platform whose largest table contains more than 4 billion rows, or may grow to a total size of 8TB or greater.
Multiuser environments, and systems with memory constraints, both benefit from an IQ page size of at least 64KB, as this size minimizes paging.
Sybase IQ stores data on disk in compressed form. It uncompresses the data and moves data pages into memory for processing. The IQ page size determines the amount of disk compression and the default I/O transfer block size for the IQ store. For most applications, this default value is best. For information on these settings and other options that affect resource use and performance, see Chapter 4, “Managing System Resources,” in Performance and Tuning Guide.
If your database includes very wide tables, you may find that the next higher IQ page size for a given number of rows gives you better performance. For example, tables with multiple columns of wide CHAR or VARCHAR data (columns from 255 to 32,767 bytes) are likely to need a larger than usual IQ page size.
Because IQ stores data in columns, it does not have a true maximum row length. The practical limit, however, is half your IQ page size, because that is the widest result set that a query is guaranteed to be able to return to the client. Choose an IQ page size at least twice the width of the widest table possible.
