Spotlight on SAP ASE 2.12 - Release Notes

Synchronous Data Reads

Reads that retrieve data pages from the database into buffer pools as part of query processing. Synchronous data reads occur when a query requires an index page that is not already in the buffer pool. The system must read these pages from disk into the buffer pool before execution of the query can continue.

Compare synchronous data reads with asynchronous data reads, in which prefetchers read data pages from the database into the buffer pool before these pages are actually needed by the query. These reads are asynchronous because they are performed outside of actual query processing. Asynchronous reads do not block query processing while data pages are retrieved.