DB2 for z/OS
IBM's relational database on the mainframe, where a great deal of the world's banking and insurance data is stored.
Also written Db2, DB2, Db2 for z/OS
DB2 for z/OS is the relational database that runs on the mainframe. IBM now writes the name as Db2, and you will see both spellings; they are the same product.
It stores data as tables of rows and columns and is queried with SQL, so anyone who has used a relational database elsewhere will recognise the model immediately. What differs is scale and the environment around it. A large DB2 system holds billions of rows and serves tens of thousands of transactions a second, with recovery guarantees to match.
It runs as a subsystem, started with the system and shared by everything on it. Batch jobs read and write it, CICS transactions read and write it, and programs in COBOL and other languages access it through SQL embedded directly in their source.
The difference from a database you might run on a laptop is mostly in the surrounding process. Access is granted through the security manager, programs are bound before they can run, and changes to table structures go through controlled release procedures.
Related terms
- SQLThe language used to query and change relational data. The same SQL used everywhere else, running against mainframe tables.
- Embedded SQLSQL statements written directly inside a COBOL program, marked off so they can be prepared before compiling.
- BINDPreparing a program's SQL for execution, working out how each statement will access the data and storing the result.
- SQLCODEThe result code DB2 returns after every SQL statement, saying whether it worked and what happened if it did not.
- SubsystemA major piece of software running under z/OS that provides a service to applications, such as a database or a transaction manager.
- IMSAn older IBM transaction manager and hierarchical database, still running some of the highest-volume systems in the world.