A spid attempts to write to a MASS, but another spid is already changing the MASS, so the first spid must wait until the changes are complete.
Adaptive Server minimizes the number of disk I/O operations it performs. If a process responsible for writing pages (for example, the checkpoint process) needs to modify a page but determines that another process is modifying the page, the second process waits until the first process completes so the page write includes the page modification.
