Strict 2PL Timeline Simulator — Deadlock Detection

Paste transactions, simulate S/X locks, and render a row‑by‑row timeline table. Locks obey shared/exclusive compatibility and S→X upgrade rules. COMMIT automatically releases all locks held by the transaction. Deadlocks are detected with a wait‑for graph; on detection a random victim is ABORTed and shown in the schedule. Tip: Schedules are bookmarkable — the input is mirrored into the page URL and loaded on refresh.

Input format — one transaction per line: T1: S(A) R(A) X(B) W(B) COMMIT. Tokens: S(X), X(X), U(X), R(X), W(X), COMMIT, ABORT. Aliases: LOCK-S, LOCK-X.

S(lock) X(lock) WAIT (blocked) U(unlock) COMMIT / ABORT (auto‑unlock)