1) What is database management system(DBMS)?
A ). Allow access to the data for multiple users from a single instance of the data. Control concurrent access to the data to maintain integrity for all updates. Minimize hardware device and operating system access method dependencies. Reduce data redundancy by maintaining only one instance of the data.
Interact with the operating system and manage the physical location of the data. Application programs that access and manipulate the data do not need to know where the data actually resides.
2) What kind of databases IMS supports?
A. Full-function database and Fast path database
3) What is full function database?
IMS full-function databases are hierarchic databases that are accessed through Data Language I (DL/I) call language and can be processed by all six types of application programs: IMS Fast Path (IFP), message processing (MPP), batch message processing (BMP), Java message processing (JMP), Java batch processing (JBP), and batch.
Full-function databases can be accessed directly by record or sequentially, and by other sequences that are planned for when the database is designed
4) What is fastpath database?
Fast Path DEDBs are designed to provide highly available data and fast processing for IMS applications, and can be processed by all types of application programs. A DEDB is a direct-access database that consists of one or more areas, with each area containing both root segments and dependent segments. DEDBs use a data structure that allows them to be used for both hierarchical processing and journaling. The database is accessed by using the VSAM Media Manager.
DEDBs are particularly suited for use where large databases or very low processing costs are required, or when high data availability or very high performance is required.
5) How data is stored in both IMSDB and DB2 databases?
A. Some business applications require that the data is kept in both IMS and DB2 for z/OS databases. One such scenario is a high-performance production application that works with the data in an IMS database and a business decision support application that works with the same data in a DB2 for z/OS database. Production applications running in IMS Transaction Manager (IMS TM) can update data that is stored in a DB2 for z/OS database and data that is stored in an IMS database. If not performed in a single, logical unit of work, coordinating these updates can be complex.
6) What is reorganization in IMSDB?
To reclaim and consolidate free space that has become fragmented due to repeated insertion and deletion of segments.
To optimize the physical storage of the database segments for maximum performance (get dependent segments that are in distant blocks, which increases physical I/O, back in the same block as the parent or root), a situation that is normally the result of high update activity on the database.
To alter the structure of the database, change the size of the database data sets, alter the hierarchical direct access method (HDAM) root addressable area, and add or delete segment types.
7) What is database recovery? when we need to need it?
Database recovery is normally performed only when there has been a failure of some sort. Most of the time, recovery is done as a result of a system, hardware, or application failure. However, you can also use recovery procedures to return a database to a previous point in time, and to recover from application logic failures.
In general, a database might need to be recovered under the following circumstances:
A DB batch update job fails after making at least one database update.
A failure occurs on a physical DASD device.
A failure occurs in a run of the Database Recovery utility.
A failure of a dynamic backout or a run of the Batch Backout utility (DFSBBO00) occurs.
An IMS online system failure and emergency restart does not complete.