Specifies the percentage of the buffer caches above the wash marker.
Can be set only for the PUBLIC group. DBA authority is required to set the option. Shut down and restart the database server to have the change take effect.
Sybase IQ buffer caches are organized as a long MRU/LRU chain. The area above the wash marker is used to sweep out (that is, write) dirty pages to disk.
In the IQ Monitor -cache report, the Gdirty column shows the number of times the LRU buffer was grabbed in a “dirty” (modified) state. If GDirty is greater than 0 for more than a brief time, you might need to increase SWEEPER_THREADS_PERCENT or WASH_AREA_BUFFERS_PERCENT.
The default setting of this option is almost always appropriate. Occasionally, Sybase Technical Support might ask you to increase this value.