# 14.1 An Interrupted Transaction _Peios / Advanced Peios / peipkg / Failure Modes_ > Power loss or a kill partway through — what the journal preserves, what happens next, and how a post-commit crash differs. The system loses power, or the process is killed, partway through an operation. ## 14.1.1 What survives The transaction's journal is rows in the package database, written before any file moved, carrying the backup map. The database is a transactional store, so the journal is either there or it is not — never half-written. ## 14.1.2 What happens next The next install, upgrade, or uninstall acquires the lock, finds the pending transaction, and rolls it back: every displaced original renamed from its backup path back into place, every directory the transaction created removed, every staged file discarded, and the transaction cleared. That happens automatically and silently. No prompt, and no audit event. ## 14.1.3 If the crash came after the commit The transaction is committed and there is nothing to recover. What is left is cleanup: staged files and backups that were never discarded. Those are siblings of their destinations under names carrying the transaction identifier, and they are removed by the cleanup step whenever it next runs. ## 14.1.4 If the transaction spanned several roots Recovery rolls forward instead. A root found pending after a sibling committed is completed from the state its journal persisted, because a committed sibling cannot be undone. A pending root carrying no persisted state can be neither completed nor safely reversed, and recovery refuses it — blocking further work in that root until `peipkg recover` is run. A pending cross-root transaction found by an ordinary single-root operation is refused rather than recovered, for the same reason. ## 14.1.5 If peipkg was upgraded in between The journal records the schema version it was written under. A peipkg that can read it recovers the transaction; one that cannot refuses, naming the schema version, and leaves it for a version that can.