1) what’s mainframe?
Mainframes systems are designed for large amounts of data in many different and interconnected ways.Mainframe is a machine that runs a mainframe operating system. In the IBM world, this operating system is z/OS, OS/390, MVS/ESA, VM/ESA and VSE/ESA.
2) what’s the advantage of mainframe?
Reliability,recoverability,redundancy,safty,connectivity,concurrency
3) what’s OS/390?
OS/390 is a new, integrated(完整的) enterprise server operating system environment. It incorporates(合并) into one product a leading-edge and open communication server, distributed (分布式的)data and file services, parallel sysplex(系统综合体) support, object-oriented programming, DCE and open application interfaces.
4) what’s the OS390′S elements ?
DFSMS,SDSF,TSO,ISPF,DITTO,NETVIEW,SDFII,VTAM,JES2,RACF etc…
5) what’s the sysplex?
SYSPLEX is a collection of MVS systems that cooperate(合幷), using certain hardware and software products, to process work.
6) how many type physical storage are there in mainframe?
Central Storage (Main Storage)
Expanded Storage
Auxiliary Storage
7) what’s jes2?
A job entry subsystem (JES) is responsible for managing jobs in an OS/390 system.
8) what’s job process stage?
Input
Conversion
Execution
Output
Hardcopy
Purge
9) what’s catalog in mainfram?
Master catalog is the catalog that lists all the user catalogs, system datasets and their locations.
User catalog is the catalog that can be accessed and changed by users. It holds the user datasets.
There are one, and only one, master catalog.
The search order of catalog is:
STEP CAT in job
JOB CAT in job
Aliases(别名) in User CAT
Master catalog
10) How many type are There several types of DUMP?
SYMPTOM DUMP
SNAP DUMP
SYSDUMP
SYSMDUMP
SVCDUMP
STAND-ALONE DUMP
11)what’s ISPF?
ISPF (Interactive System Productivity Facility) is PDF (Program Development Facility)’s prerequisite(首先必备的) licensed program. ISPF must be installed either before or during the installation of PDF.
12) What is JCL ?
JCL stands for Job Control Language, JCL is a set of control statement that provide the specification necessary to process a job.
13) What is the difference between keyword and positional parameters ?
Positional parameters are characterized(表現特色) by their position in the operand(操作數) field in relation to other parameters.
Keyword parameters are positionally independent with respect to others of their type and consisting of a keyword followed by an equal sign and variable information.
14) What is a DISP ?
DISP is a keyword parameter which is defined on the DD statement and which consist of the following positional subparameters: DISP=(Status, Normal Disp, Abnormal Disp). The DISP parameter describes the current status of the dataset (old, new, or modified) and directs(指示) the system on the disposition(部署) of the data set (pass, keep, catalog, uncatalog, or delete) either at the end of the step or if the step abnormally terminates(. DISP is always required unless the data set is created and deleted in the same step.
15) What is DISP=SHR ?
DISP=SHR permits old data sets to be shared. SHR is identical(同样的) to OLD except that several jobs may read the dataset concurrently(并发的) in multiprogramming(多道程序设计) environments. SHR must be used only for input data sets; use OLD or MOD if data set is modified.?Sharing data set is necessary because public libraries like SYS1.LINKLIB or the subroutine(子程序) libraries should be available to every job in the system.
16) What is DISP=MOD ?
DISP=MOD modifies a sequential(顺序的) data set. It is a convenient(方便的) way to add data to the end of sequential dataset. If the data set doesn’t exist, the system changes MOD to NEW unless the VOL parameter request specific volume. When VOL is coded, the system expects to find data set on the specified volume and terminates the step if it cannot find it. MOD is the usual way of extended data sets in to several direct-access(随机存储) volumes.
17) What is DISP=PASS ?
PASS passes the data set on to subsequent(后来的) job steps, and each step can use the data set once. It is a positional subparameter of the DISP which could only be specified under normal termination action. Pass saves time because the system retains(保留) the data set location and volume information.
18) What are the parameters that have to be coded on a DD statement in order to retrieve(找回) a cataloged data set ?
The minimum parameters needed are DSN and DISP.
19) How does the system get information about the block size ?
DCB info comes from :-
1) Program - FD: BLOCK CONTAINS 3 RECORDS RECORD CONTAINS 100 CHARACTERS
2) The label - like a tape
3) From the VTOC - for Dasd
4) From the JCL - DCB=BLKSIZE=nnn.
20) What is a Label ?
LABEL is a keyword parameter which can be specified on DD statement and consists of the following subparameters:
LABEL=(Relative File #, Type of Label Processing)
The LABEL parameter tells the type of label, the relative file number,and whether the data set is to be protected for input or output.
21) When should be NL be specified as a type of label processing ?
NL should be specified when a program needs to process unlabeled tapes, NL can also be specified when the pgm wants to create unlabeled tape because the system’s default action, in cases(万一) when parameter is not specified, will create IBM standard label. Nonlabeled tapes are often used for sending tapes to another installation. That way you don’t have to worry about the tape label corresponding(相应的) to the standards at the other installation or about accidentally matching the volume serial(连续的) number of an existing tape at the installation.
22) How do you describe the input data which is a part of the input job stream ?
You should use either DD * or DD Data.
23) What is the difference between * and Data ?
DD * and DD DATA describe the input data which follows the above mention cards. If the input data contains record switch // in col 1 and 2 then DD Data should be used.
24) What is the purpose of SPACE parameter ?
It is a keyword parameter which should allocated(分配) he DD statement for the output data sets stored on the disk.It consists of the following subparameters:
SPACE=(BLKS/CYL/TRK,(primary,secondary,index),RLSE,CONTIG)
25) What is a RLSE ?
RLSE releases all unused space when the data set is closed. It permits you to allocate more space than perhaps, it needed without wasting space. Space is released only if the data set is not empty and if the data set is closed after being opened.
26) What is a CONTIG ?
CONTIG requests the primary space be allocated only on contiguous tracks and cylinders, that is all tracks on a cylinder are contiguous, and if more than one cylinder is needed, the cylinders are also contiguous. Always code CONTIG if track overflow is used. Contiguous-连续的
27) What is a PDS ?
PDS is a library type of data set organization consisting of Directory and Members. The directory consists of blocks, and each block is 256 bytes in length and can hold up to 5 members. Each member of the PDS is a sequential data set.
28) What is a Temporary Data Set ?
Temporary data sets are used for storage needed only for the duration of the job. If the DISP parameter doesn’t delete the data set by the end of the job, the system will delete it. Deleting a tape data set dismounts the tape, whereas deleting a dataset on a direct-access volume release the storage. A data set is marked temporary by omitting the DSN parameter or by coding DSN=&&dsname. The system assign a unique name to the data set when the DSN parameter is omitted, and any subsequent steps using the dataset refer back to the DD statement. Refer-提交
29) What is COND parameter ?
It is a keyword parameter which can be specified on the JOB or EXEC statements. COND consists of 3 subparameters:
code(0 thru 4095),logical operator, and stepname of the step that is going to be compared.
The purpose of the COND is to determine whether the step should be executed or bypassed. If condition specified in the COND parameter is true,the step is bypassed.
30) How do you specify a COND parameter for a job step so that the step will never be executed ?
COND=(0,LE) or COND=(4095,GE).
31) What does COND=ONLY mean ?
It means that this job step will be executed only if a previous step had abnormally terminated.
32) What does COND=EVEN mean ?
It means that this jobs step will be executed even if a previous step abnormally terminated.
33) What is a NAME ?
Name is a positional parameter which identifies the person or group responsible for a job.
34) What is a PRIORITY ?
It is a keyword parameter which specifies a job initiation priority within its job class. When the job is initiated, the system will convert the job’s priority into a dispatching priority so that job’s task can complete with other tasks for use of main storage and CPU resources.
35) How does the system determine the priority of a job for execution ?
First the system determines which job has the highest class. Each class has a job queue with jobs of different priorities. The system will select the job for execution that has the highest PRTY (0 thru 15) 15 is the highest priority.
36) What is a MSGCLASS parameter ?
It is a keyword parameter which specifies the output class to which system messages for your job are to be routed. Output class is an alphabetic (A thru Z) or numeric (0 thru 9) character. The default for MSGCLASS parameter will be A. System messages and output data sets can be routed to the same output class. You can code the MSGCLASS parameter in the Job statement and the SYSOUT parameter on the DD statement.
37) What is MSGLEVEL parameter ?
It is a keyword parameter which indicates what job output is to be written as a part of output listing. The following outputs can be requested: the Job statement;
all input job control statements;
allocation, disposition and allocation recovery messages(allocation/termination message)
MSGLEVEL=(statements, messages)
Statements:
- 0 - only the job statement is to be written;
- 1 - all input control statements, cataloged procedure statements and the internal representation of procedure statement parameters after symbolic parameters substitution are to be written;
- 2 - only input job control statements are to be written;
Messages:
- 0 - No allocation/termination messages are to be printed unless the job terminates abnormally;
- 1 - All allocation/termination messages are to be printed.
38) How can you check for syntax or JCL errors without actual execution of a job ?
TYPRUN=SCAN should be specified on a job card
39) What is the difference between the COND parameter specified on the EXEC statement and the one specified on the JOB statement ?
COND parameter specified on EXEC statement determines whether step should be bypassed or executed.
COND parameter defined on the JOB statement will determine whether Job should be terminated at a certain point or continued. When COND parameter is defined on the JOB statement, the system evaluates condition specified in the COND parameter before beginning of any job step and compares the code specified in the COND parameter with the return code of all previous jobsteps. If that condition is true, the rest of the job steps are bypassed.
40) What’s job card?
Every job will begin with a ‘Job Card’, which specifies the jobname, and other important information about how the job will execute.
Every job you code will have a Job Card. This is the first thing you must code for every job.
41) how many info are there in job statement?
-Accounting Information
-Programmer
-Class
-Message Class
-Storage Required
-Conditional Testing
-Notify
-Message Level
-Time
-Other Information
42) what’s track? And size?
Mainframe storage Unit: a track = 56664bytes=55.34KB
43) What’s DUMMY dataset?(虚拟的)
The special DD statement (DD DUMY) enables you to ignore a dataset for the current program execution.
44) what’s difference between joblib and jcllib?
JOBLIB:Identify a private library that the system is to search for the program named in each EXEC statement PGM parameter in the job. Only if the system does not find the program in the private library, does it search the system libraries.
JCLLIB:
Identify the names of the private libraries that the system uses for the job. The system searches the libraries for: Procedures named on any EXEC statements
Identify the names of the system procedure libraries and installation-defined
procedure libraries that the system uses for the job.
Identify the order in which the libraries are to be searched. The system
searches the libraries in the order in which you specify them on the JCLLIB
statement, prior to searching any unspecified default system procedure
libraries.
45) What’s differnce between in-stream procedure and catelog procedure?
In-stream procedure is storaged in a job,however cataloged procedure is separated into a private library or PDS.
46) what’s is COBOL?
COmmon Business Oriented Language, a structure language for massive regularity datum processing.
47) how many type are there in cobol call procedure?
STATIC: static is included in the global link of the program, the subroutine linked in to main program and always resident
DYNAMIC: separately linked proram are called with the program name in quotes, and the subroutine are loaded into memory only when called by calling program.
48) why use an internal sort?please explain the COBOL internal sort?
sort file name on ascending key-allow you to include logic to be preformed before and after sort, to alter datum immediately before sorting it/reduce need for separate programs.
In JCL allocate sort work space, in data division code SD, in procedure division use SORT statement with the ascending/descending key, using/ input procedure.
Please add a example done before.
49) Please distinguish “go to”, “exit”, “stop run”, “go back”, “continue”?
as book
50) How many different level numbers can be used in COBOL to describe a record?
01-49
51) Q What is level 88?
A The level 88 in the Data Division can be used to give condition names to the values that a field contain. When this level is specified you can use the condition name instead of is = to in the IF statement. Condition name should be specified under Level 88 immediately following the field description.
52) What is the difference between level 77 and 01? and which is more efficient?
A Level 77 can be used to describe independent elementary items in the Working-Storage or Linkage Sections.
Level 01 can be used to describe both elementary and group items. Any item described in Level 01, the system is putting on Double-Word boundary and inserts slack bytes if necessary
53) Name the different PERFORM statement?
PERFORM
PERFORM THRU
PERFORM ‘n’ of TIMES
PERFORM UNTIL
PERFORM VARYING with UNTIL Option.
54) What is a subscript?
A Subscript represents occurrence # of the Table Entry. Subscript can be represented explicitly and implicitly. Explicitly means thru occurrence # of the table entry; implicitly means thru a data name. That data name should be defined as an independent item in the W-S Section. The most efficient definition of Subscript is Full-Word binary.
55) What is an index?
Index is assigned to specific table thru INDEXED BY clause. Internally is represented by Index Register which is Full-Word binary. Specific index name can be used to reference a field from the table to which that index is assigned to index represents displacement value of the table entry from the beginning of the table.
56) What are the different ways of an internal table search?
a. Sequential Search statement. (SEARCH)
b. Binary search statement.(SEARCH ALL)
57) What is the difference between SEARCH and SEARCH ALL?
A Serial search (SEARCH) examines each table entry starting at the beginning, whereas a binary search (SEARCH ALL) starts looking at the mid-point of the table and works its way toward the argument depending upon if its too high or too low. A serial search can be used for unsorted tables, while a binary search is only useful if the tables is sorted.
58) How do change the value of an index in a COBOL programs?
A SET statement.
59) How many different data USAGEs can be used in COBOL?
DISPLAY, COMP, COMP-3, INDEX, POINTER.
60) in CICS MAP field, what’s the DFHMDF’s L indicator variable ?
61) what’s the conversation transaction?
programs share the same procedure division but have separate working
storage
62) what’s non-conversation transaction?
program is not kept in main storage while waiting for input from
terminal/program is transaction driven /release resources between executions of a task information passed
between programs and task via commarea or temporary storage
63)Please explain the following concept and abbreviation:
PCT
PPT
JCT
SNT
SIT
FCT
TCT
DCT
PCT PROGRAM CONTROL TABLE
TRANSACTIONS
One entry for every type
PPT PROGRAM PROCESSING TABLE
PROGRAMS/MAP SETS
Use count
JCT JOURNAL CONTROL TABLE : record system log and users’ journal
JOURNALS
SNT SIGN ON TABLE :define users’ right
SIT SYSTEM INITIALIZATION TABLE:set cics system initialized parameter
FCT FILE CONTROL TABLE:define all files that are used in cics
TCT TERMINAL CONTROL TABLE :define terminal and system connections
DCT DESTINATION CONTROL TABLE
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