Useless Actions Make a Difference: Strict Serializability of Database Updates

Ravi Sethi

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


When several transactions read and write tems in a database, the question of consistency of the database arises. Consistencys maintained if transacUons are serial, the read and write acuons of a transacuon execute completely before the actions of the next transaction begin A particular history of interleaved read and write actions belonging to several transactionss correct if its equivalent to a serial history. Since senahzablhty of hlstones is known to be NP-complete, subclasses of senahzable histories have been stu. One such class consists of htstones senahzable in a strict sense, transacuons that are already m serial in a history must remain m the same relative order When there are no useless actions m a history, it is shown that strict sermlizabdity can be determined m polynomial time If useless actions are permitted, then strict serializabihty becomes NP-complete The above results apply to two-step transactions m which theres a read step followed by a wnte step Each step revolves some subset of the items m the database. With mulustep transactions stnct senahzabdtys NP-complete even ff there are no useless actions.

Original languageEnglish (US)
Pages (from-to)394-403
Number of pages10
JournalJournal of the ACM (JACM)
Issue number2
StatePublished - Apr 1 1982


  • Concurrency control
  • models of transactions

ASJC Scopus subject areas

  • Software
  • Control and Systems Engineering
  • Information Systems
  • Hardware and Architecture
  • Artificial Intelligence


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