IBM manual VSE to OS/390 Migration Workbook

Job Entry Subsystem. An MVS subsystem that receives jobs into the system, converts them to internal format, selects them for execution, processes their output, and purges them from the system. In an installation with more than one processor, each JES2 processor independently controls its job input, scheduling, and output processing.

job step. You enter a program into the operating system as a job step. A job step consists of the job control statements that request and control execution of a program and request the resources needed to run the program. A job step is identified by an EXEC statement. The job step can also contain data needed by the program. The operating system distinguishes job control statements from data by the contents of the record.

job stream. The sequence of representation of jobs or parts of jobs to be performed, as submitted to an operating system. Synonymous with input stream, run stream.

journaling. The process of recording changes made in a physical file member in a journal. Journaling allows the programmer to reconstruct a physical member by applying the changes in the journal to a saved version of the physical file member.

Julian date. As a general term used widely in computer programming and this document: A date in the format YYDDD. A date format that contains the year in positions 1 and 2, and the day in positions 3 through 5. The day is represented as 1 through 366, right adjusted, padded with zeroes on the left. For example, 1996-August-29 is 96242.

However, the above definition is accurately referred to as the Ordinal Day of Year date, and an accurate definition of Julian Day Number is as follows:

The astronomical system that counts the days since the First of January in the year 4713 BCE (the year

−4712 before the common era). This scheme was invented by the astronomer Joseph Scaliger in the 16th century and named by him for his father Julius. The leap year reforms implicit in the new scheme were adopted at the command of Pope Gregory XIII in the year 1582 - hence the Gregorian Calendar. The Gregorian, or New Style, calendar was adopted in Britain and their colonies in September of 1752. (September of that year was missing 11 days. The 14th followed the 2nd.)

The remainder left when dividing the Julian Day Number by 7 indicates the day of week of the specified date. Zero corresponds to Monday, 1 to Tuesday, up through 6 for Sunday.

For example, 1996-Aug-29 is equivalent to Julian Day 2450325. Further, the hour of the day is expressed as a decimal such that 2450325.5 is midnight

1996-Aug-29, based on the fact that a Julian Day begins at midday (noon).

K

key field. (1) In VSAM, a field, located in the same position in each record of a file or data set, whose content is used for the key of a record. (2) In IMS/VS, the field in a database segment used to store segment occurrences in sequential ascending order. A key field is also a search field. Synonymous with sequence field.

key-sequenced data set (KSDS). A VSAM file or data set whose records are loaded in key sequence and controlled by an index.

L

label area. Synonym for label information area

label information area. In VSE, an area on a direct access storage device that stores label information read from job control statements or commands.

Synonymous with label area.

Leap year. A year either evenly divisible by 400 or evenly divisible by 4 and not evenly divisible by 100. For example, the years 1700, 1800, 1900, and 1995 are not leap years, but the years 1600, 1996, and 2000 are leap years.

librarian. In VSE, the set of programs that maintains, services, and organizes the system and private libraries.

library member. In VSE, the smallest unit of data that can be stored into and retrieved from a sublibrary.

licensed program (LP). A separately priced program and its associated materials that bear an IBM copyright and are offered to customers under the terms and conditions of either the Agreement for IBM Licensed Programs (ALP) or the IBM Program License Agreement (PLA).

Lilian date. The number of days since

1582-October-14. 1582-October-15 is Lilian day 1,

1582-October-16 is Lilian day 2, and so on. (Named for Aloysius Lilius (an advisor to Pope Gregory XIII) who, together with his brother, constructed the current Gregorian calendar.)

link pack area (LPA). In OS/390, an area of main storage containing reenterable routines from system libraries. Their presence in main storage saves loading time.

linkage editor. A program that resolves

cross-references between separately assembled object modules and then assigns final addresses to create a single relocatable load module. The linkage editor then stores the load module in a program library in main storage.

574VSE to OS/390 Migration Workbook