| 摘要 |
<p>ASEG (segment) subsystem of a parallel database extension (PDE) provides services for creating, manipulating, and destroying access to data segments in address space. The SEG subsystem works with transient segments (also referred to as scratch segments) that are created as offsets in a "well-known" file created during initialization of the PDE. The offsets are stored in objects/elements in a queue in the virtual address space of the SEG subsystem. Upon partitioning addressable memory into one or more scratch segments, obtaining the offsets for the scratch segments, and mapping the offsets into the SEG system's virtual address space, the physical memory is locked. When the scratch segments are needed, an element/object from the queue containing the appropriate size scratch segment is mapped into the requestor's address space. Once mapped to the requestor's address space, the element is unmapped from the SEG's virtual address space. Thereafter, the requestor can utilize the scratch segment as desired (in accordance with the access granted by the SEG subsystem).</p> |
