First consider the following simple example calls to a WT instance with the same key:

• Write + Commit U1 at TS(20)
• Prepare U2 at TS(10)
• Commit U2 at any commit + durable timestamp (the exact values irrelevant)

When using the (patched, see WT-7815) ordered write timestamp assertion, WT will correctly call out this misuse when the transaction commits entirely because of the chosen prepare timestamp.

Now consider the same example, but with a restart:

• Set OldestTimestamp 1
• Write + Commit U1 at TS(20)
• Set StableTimestamp 20
• Take a stable checkpoint and restart WT
• Prepare U2 at TS(10)
• Commit U2 at any commit + durable timestamp

In the second example, the assertion does not fire, but this out of order usage is still problematic and must be avoided from unintentionally happening.