Simple Transaction Abort
For now, consider an explicit abort of a Xact.
We want to “play back” the log in reverse order, UNDOing updates.
- Get lastLSN of Xact from Xact table.
- Can follow chain of log records backward via the prevLSN field.
- Before starting UNDO, write an Abort log record.
- For recovering from crash during UNDO!