In database concurrency control, lock granularity refers generally to:
2012
In database concurrency control, lock granularity refers generally to:
Answer: B. The size or scope of the data item to which one lock applies — Concept — Lock granularity is the size or scope of the data unit controlled by a single lock. A lock may cover a database, file, record, page, or smaller…
- A.
The storage capacity of the entire database
- B.
The size or scope of the data item to which one lock applies
- C.
The byte length of one record
- D.
The byte length of one file
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Correct answer: B
Concept — Lock granularity is the size or scope of the data unit controlled by a single lock.
A lock may cover a database, file, record, page, or smaller item; larger units are coarser and smaller units are finer.
Application — The stem asks for the general locking meaning, so size means the scope of the item controlled by one lock, not a byte count.
The applicable unit is a data item. Depending on the locking scheme, that item may be a database, file, page, record, field, or another unit.
Contrast — The other values describe physical storage measurements rather than the general lock-scope definition:
The storage capacity of the entire database is a physical byte-count property, not the general lock-scope definition.
The byte length of one record is a physical size property of a particular record.
The byte length of one file is a physical size property of a particular file.
Cross-check — Changing from database-level locking to record-level locking changes the amount of data controlled by one lock even if no stored byte count changes.
Result — Therefore, lock granularity denotes the size or scope of the data item treated as one locking unit.