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Overview of z/OS Online Workloads

Explore the role of large systems in online businesses, including attributes of transactional systems and the use of databases. Learn about network connectivity models and the importance of DBMS in ensuring consistency, security, and efficient data management.

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Overview of z/OS Online Workloads

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  1. Chapter 10 Overview of z/OS online workloads

  2. Chapter 10 objectives • Be able to: • Describe the role of large systems in a typical online business. • List the attributes common to most transactional systems. • Explain how databases are used in a typical online business. • Describe two models for network connectivity for large systems.

  3. DBMS multithreading multitasking root segment SQL thread transaction Key terms in this chapter

  4. Example of online processing: a travel agency • Mainframe applications designed for: • employee and customer information • contacts with car rental companies • hotels • airline schedules • Changes must be immediately reflected to application end-users (in real time) • Contrast with batch processing

  5. Example of online processing (continued)

  6. A practical example

  7. Transactional systems • Requirements: ACID • Atomicity • Consistency • Isolation • Durability

  8. Transactional systems: terminology • Commit and roll back • Multitasking and multithreading • Thread • Reentrancy

  9. Characteristics of a transactional systems

  10. Two-phase commit

  11. What is a database?

  12. Why use a database? • Reduce programming effort • Manage data more efficiently • Easy to separate confidential/sensitive info • Provide a greater level of security • Access & update simultaneously • Ensure consistency • Provide backup and recovery • Utilities to monitor and tune • Structure change does not impact existing developments

  13. Role of the database administrator

  14. Databases: terminology • Entities • Data attributes • Entity relationships • Application functions • Access paths

  15. Databases on z/OS • Hierarchical databases, such as IMS • Relational database management system (RDBMS), such as DB2

  16. Hierarchical DB : Relationships & sequence

  17. Hierarchical data structure

  18. Segment types and their relationships

  19. Relational DBMS: Codds relational principles • Primary key • Referential Integrity • Easy to use query language • Nulls • Normalization/Denormalization • 1NF: structure of a table • 2NF: 1-to-1 • 3NF: 1-to-many relationships • 4NF, 5NF: many-to-many relationships

  20. Relational DBMS: data structures and SQL • Data Structures • Databases • Tables : column, row and value • Indexes • Keys • Primary Key • Unique Key • Foreign Key • SQL • DML: SELECT, UPDATE, INSERT, DELETE • DDL: CREATE, ALTER, DROP • DCL: GRANT, REVOKE

  21. A database comparison: • IMS: • Data is relatively static • Navigational : need to know the structure to get to the right data • DB2: • Changeable info • Change in structure : no impact on existing application • Non-Navigational : no need to know the structure to get to the right data (just tablename and columnname(s))

  22. Summary • Interaction with the computer happens online through the help of a transaction manager. • Many transaction managers and database managers exist, but their principles are similar. • Data can be stored in a flat file, but this can result in duplication or inconsistent data. It is better to create central databases, which can be accessed (reading and changing) from different places. • The handling of consistency, security, etc. is done by the database management system.

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