Which statement describes how the relay log works?

Question

Options

• AWhen a slave receives a change from the master, it is processed first, and then recorded in the relay log.
• BIt maintains a record of available master binary logs and the current executed log position.
• CIt stores changes on the master, and relays them to the slave.
• DWhen a slave receives a change from the master, it is recorded in the relay log first and processed later.

• A
  3% (1)
• B
  93% (27)
• C
  3% (1)

Explanation

Option B as marked appears to be incorrect based on how MySQL replication actually works - option D is the accurate description of the relay log. This looks like a question with a marking error, so here's an accurate breakdown to protect your exam performance:

Why D is correct: The relay log sits on the slave server. The I/O thread receives binary log events from the master and writes them to the relay log first; then the SQL thread reads that relay log and applies (processes) the changes afterward. Record first, execute second - that's the relay log's role.

Why the other options are wrong:

• A reverses the order - changes are never processed before being recorded in the relay log.
• B describes what the master.info file (or mysql.slave_master_info table) tracks - the master's available binary logs and the current replication position - not the relay log itself.
• C confuses the relay log with the master's binary log. The binary log lives on the master; the relay log lives on the slave.

Memory tip: Think of the relay log as a inbox on the slave - mail (changes) arrives and sits in the inbox (relay log) before you open and act on it (SQL thread applies it). The binary log is the outbox on the master.

If this question appears on your actual exam with B marked correct, it may reflect a flawed question - but knowing that D is the technically accurate answer is what matters for understanding MySQL replication.

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