1Z0-052 · Question #58
Which is the correct description of a pinned buffer in the database buffer cache?
The correct answer is A. The buffer is currently being accessed. A pinned buffer in the Oracle database buffer cache is one that is actively being accessed by a session, preventing it from being evicted. It is held in place until the accessing process releases it.
Question
Which is the correct description of a pinned buffer in the database buffer cache?
Options
- AThe buffer is currently being accessed
- BThe buffer is empty and has not been used
- CThe contents of the buffer have changed and must be flushed to the disk by the DBWn process
- DThe buffer is a candidate for immediate aging out and its contents are synchronized with the block
How the community answered
(43 responses)- A88% (38)
- B7% (3)
- C2% (1)
- D2% (1)
Why each option
A pinned buffer in the Oracle database buffer cache is one that is actively being accessed by a session, preventing it from being evicted. It is held in place until the accessing process releases it.
When a server process reads or modifies a data block, it pins the corresponding buffer to signal to the buffer manager that the buffer is in use. The buffer cannot be selected for replacement or aged out of the cache while it remains pinned, ensuring data consistency during active access.
An empty, never-used buffer is called a free buffer, not a pinned buffer.
A buffer whose contents have been modified but not yet written to disk is classified as a dirty buffer, managed by the DBWn process.
A buffer at the least-recently-used end of the LRU list that is eligible for replacement is described as a candidate for aging out, not a pinned buffer.
Concept tested: Oracle buffer cache buffer states - pinned vs dirty vs free
Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/memory-architecture.html
Topics
Community Discussion
No community discussion yet for this question.