tailieunhanh - Database Management Systems: Chapter 4 - Introduction to Transaction Processing Concepts and Theory

Database Management Systems: Chapter 4 - Introduction to Transaction Processing Concepts and Theory Introduction to Transaction Processing, Transaction and System Concepts, Desirable Properties of Transactions, Characterizing Schedules based on Recoverability. | Chapter 4 Introduction to Transaction Processing Concepts and Theory Adapted from the slides of “Fundamentals of Database Systems” (Elmasri et al., 2003) Chapter Outline 1 Introduction to Transaction Processing 2 Transaction and System Concepts 3 Desirable Properties of Transactions 4 Characterizing Schedules based on Recoverability 5 Characterizing Schedules based on Serializability 6 Transaction Support in SQL 1 Introduction to Transaction Processing(1) Single-User System: At most one user at a time can use the system. Multiuser System: Many users can access the system concurrently. Concurrency Interleaved processing: concurrent execution of processes is interleaved in a single CPU Parallel processing: processes are concurrently executed in multiple CPUs. Introduction to Transaction Processing (2) A Transaction: logical unit of database processing that includes one or more access operations (read -retrieval, write - insert or update, delete). A transaction (set of . | Chapter 4 Introduction to Transaction Processing Concepts and Theory Adapted from the slides of “Fundamentals of Database Systems” (Elmasri et al., 2003) Chapter Outline 1 Introduction to Transaction Processing 2 Transaction and System Concepts 3 Desirable Properties of Transactions 4 Characterizing Schedules based on Recoverability 5 Characterizing Schedules based on Serializability 6 Transaction Support in SQL 1 Introduction to Transaction Processing(1) Single-User System: At most one user at a time can use the system. Multiuser System: Many users can access the system concurrently. Concurrency Interleaved processing: concurrent execution of processes is interleaved in a single CPU Parallel processing: processes are concurrently executed in multiple CPUs. Introduction to Transaction Processing (2) A Transaction: logical unit of database processing that includes one or more access operations (read -retrieval, write - insert or update, delete). A transaction (set of operations) may be stand-alone specified in a high level language like SQL submitted interactively, or may be embedded within a program. Transaction boundaries: Begin and End transaction. An application program may contain several transactions separated by the Begin and End transaction boundaries. Introduction to Transaction Processing (3) SIMPLE MODEL OF A DATABASE (for purposes of discussing transactions): A database - collection of named data items Granularity of data - a field, a record , or a whole disk block (Concepts are independent of granularity) Basic operations are read and write read_item(X): Reads a database item named X into a program variable. To simplify our notation, we assume that the program variable is also named X. write_item(X): Writes the value of program variable X into the database item named X. Introduction to Transaction Processing (4) READ AND WRITE OPERATIONS: Basic unit of data transfer from the disk to the computer main memory is one block. In general, a .