Information Systems

Index • Index is a separate entity • It is organized similar to data component (CI and CA) • It has a different CI size • VSAM builds index when data is loaded • Index is organized as inverted binary tree • VSAM compresses key to conserve space • Can have several levels of indexes [...]

Cluster • It is a collection of physical data sets that makeup one logical data set • The concept of a cluster is more suited for a KSDS • A KSDS cluster has two data sets. One holds actual data records and other contains an index component • Index component permits direct retrieval of data [...]

Entry sequential data set (ESDS) • Records in an ESDS are stored in the order in which they are written and are retrieved by addressed access • Records are loaded irrespective of their contents and their byte address cannot be changed • ESDS is also referred to as a sequential VSAM data set. This is [...]

VSAM is a high-performance access method used in OS/VS & ZOS operating systems. VSAM software resides in virtual storage along with the program that needs its services for the manipulation of data on a direct access storage device (DASD). VSAM acts an interface between Operating system and application program The access method is used to [...]

Instream procedures • Completely contained within a JCL JOB • String of JCL statements appearing between a proc and pend statement within a JOB • Available to only one JOB • Upto 15 procedures can be defined within a JOB • Within a JOB, can be invoked any number of times Cataloged Procedures • A [...]

JOBLIB • Used to identify a program library to search first when attempting to locate programs executed during job’s life • Must be placed after the JOB statement and before the first EXEC statement in the JOB • More than one program library can be concatenated after the first one on a joblib JCLIB • [...]

Job Control Language or JCL is a set of control statements that provide the specifications necessary to process a job. Communication with the OS is by typing commands or Job Control Language statements. Role of JCL We do not use JCL to write computer programs. Instead, it consists of control statements that introduce a computer [...]

Z/Os architecture includes all of ESA/390 and the following extensions • IBM’s high-end server OS • Robust IBM e-server Z series mainframe OS for e-business • Highly secure scalable high performance base to deploy internet + java technology-enabled applications • Z/OS takes advantage of latest open s/w technologies like EJB/XML/HTML/UNICODE/IP network etc. • Cryptographic services [...]

Disk operating systems/360 • Single task (only one program at a time) • Simple OS, with minimum storage and CPU requirements OS/360 for system/360 • PCP (Primary control program) ran only one task at a time • Multiple fixed tasks – up to 15 tasks, with fixed time-slices for each task • Partitions have to [...]

Virtual storage • It is a technique that lets a processor simulate a large amount of main storage from a smaller installed main storage. • Implementation: Uses disk storage as an extension of main storage • At any point in time, only one program and its data is required in the main storage Multiprogramming • [...]