Transactional Systems. Why transactional systems are relevant. Examples of transactional systems: financial applications, banks, online order-entry (e-commerce), online booking, "wall-street applications". Notion of "transaction". ACID properties: atomicity, consistency, isolation, durability. Concurrency control theory. Histories (or schedules), serializability, various notions of equivalence, complexity of testing. View-serializability, conflict-serializability. Two phase locking. Hierarchical locking. Deadlock analysis and resolution. Timestamp-based concurrency control. Multi-version concurrency control. Implementation of locking in commercial systems. Reliability control theory. Notion of: stable storage, logging, checkpointing, write-ahead log rule, commit rule. Recovery protocols: warm restart, cold restart. Implementation of reliability control in commercial systems. Commit protocols, theory of two-phase-commit, presumed-abort and read-only optimizations, non-blocking protocols (3 and 4 phase commit protocols). Implementation of commit protocols with heterogeneous DB servers in the X-open standard. Database architectures. Client-server applications (two and three tiers). Heterogeneous access via ODBC-JDBC standards. Distributed databases. Notion of fragmentation, allocation, transparent access. Query optimization. Distributed transactions. Parallelism in database servers. Shared-memory vs shared-nothing approaches. Scale-up, speed-up, benchmarking of performance. Replicated databases. Synchronous vs asynchronous methods. Symmetric vs primary-secondary approaches. Implementation of replication servers. Internal structure of a database server. Buffer Management. Page management. Data organizations according to the sequential, direct, and indexed data structures. B and B+ trees. Hashing functions. Access methods: scans, ordering joins. Join methods. Query optimization fundamentals. Cost models and optimal query plan selection (branch&bound method for execution plan selection). Database administration in commercial systems. Hints to physical database design (index selection, primary storage method selection). XML Databases. XML as a data modeling paradigm. Native vs relational storage. Query languages for XML. XPath, XQuery, XQBE. Active databases: The ECA Paradigm (event/condition/action) and data management. Execution methods for active databases. Trigger languages and systems: Starburst, Oracle, DB2. Formal properties of active rule sets. Termination, confluence, observable determinism. Rule analysis. Design of active rules for integrity maintenance.
