A critical section is a working memory area to which the database system synchronizes access of competing tasks through special semaphores (regions, reader-writer-locks)
Name |
Used for |
Description |
---|---|---|
Region |
Data Cache |
EXCLUSIVE When a task accesses a critical section, the associated region blocks this critical section for all other tasks. |
Reader-writer lock (share lock) |
Catalog Cache Shared SQL Cache |
EXCLUSIVE or SHARED If a task write-accesses a critical section, the associated reader-writer lock (share lock) blocks this critical section for all other write-accesses but allows other read-accesses. If a task read-accesses a critical section, the associated reader-writer lock (share lock) blocks this critical section for all other write-accesses but allows other read-accesses. |
Concepts of the Database System, Working Memory Areas
Database Administration in CCMS, Critical Sections