JCL FAQs/Interview questions (part-1)

Q1.   What are the kinds of job control statements?
A1.    The JOB, EXEC and DD statement.

Q2.  What is the meaning of keyword in JCL?  What is its opposite?
A2.  A keyword in a JCL statement may appear in different places and is recognized by its name, eg.MSGCLASS in the JOB statement.  The opposite is positional words, where their meaning is based on their position in the statement, eg. in the DISP keyword the =(NEW,CATLG,DELETE) meanings are based on first, second and third position..

Q3.  Describe the JOB statement, its meaning, syntax and significant keywords.
A3.  The JOB statement is the first in a JCL stream.  Its format is // jobname, keyword JOB, accounting information in brackets and keywords, MSGCLASS, MSGLEVEL, NOTIFIY,CLASS, etc.

Q4.  Describe the EXEC statement, its meaning, syntax and keywords.
A4.  The EXEC statement identifies the program to be executed via a PGM=program name keyword.  Its format is //jobname EXEC PGM=program name.  The PARM= keyword can be used to pass external values to the executing program.

Q5.  Describe the DD statement, its meaning, syntax and keywords.
A5.  The DD statement links the external dataset name (DSN) to the DDNAME coded within the executing program.  It links the file names within the program code to the file names know to the MVS operating system.  The syntax is // ddname DD DSN=dataset name.  Other keywords after DSN are DISP, DCB, SPACE, etc.

Q6. What is a PROC? What is the difference between an instream and a catalogued PROC?
A6.  PROC stands for procedure.  It is 'canned' JCL invoked by a PROC statement. An instream PROC is presented within the JCL; a catalogued PROC is referenced from a proclib partitioned dataset.

Q7. What is the difference between a symbolic and an override in executing a PROC?
A7.  A symbolic is a PROC placeholder; the value for the symbolic is supplied when the PROC is invoked, eg. &symbol=value.  An override replaces the PROC's statement with another one; it substitutes for the entire statement.

Q8. What is RESTART? How is it invoked?
A8.  RESTART is a JOB statement keyword.  It is used to restart the job at a specified step rather than at the beginning.

Q9. What is a GDG? How is it referenced? How is it defined? What is a MODELDSCB?
A9.  GDG stands for generation data group.  It is a dataset with versions that can be referenced absolutely or relatively.  It is defined by an IDCAMS define generation datagroup execution.

Q10. Explain concatenating datasets.
A10.  Datasets can be grouped in a DD statement one after another, eg. in a JOBLIB statement where the load module can exist in one of many datasets.

Q11. What is the difference between specifying DISP=OLD and DISP=SHR for a dataset?
A11.  DISP=OLD denotes exclusive control of the dataset; DISP=SHR means there is no exclusivity.

Q12. What is MOD and when would you use it?
A12.  DISP=MOD is used when the dataset can be extended, ie, you can add records at the end of an existing dataset.

Q13. What are the keywords associated with DCB?  How can you specify DCB information?
What is the OS precedence for obtaining that DCB information, ie. where does the system look for it first?
A13.  The keywords associated with the DCB parameter are LRECL, RECFM, BLKSIZE and DSORG.  The DCB information can be supplied in the DD statement.  The sysem looks for DCB information in the program code first.

Q14.  How do you designate a comment in JCL?
A14.  The comment statement is //*  followed by the comments.

Q15.  What is the meaning of the EXEC statement keyword, COND?  What is its syntax?
A15.  COND specifies the conditions for executing the subsequent job step.  The value after the COND=  is compared to the return codes of the preceding steps and if the comparison is true, the step is bypassed.  (If this answer confuses you, welcome to the club - memorize it and don't ask questions!)

Q16.  What is the improvement to COND= in the latest version of MVS?
A16.  MVS now allows for an IF bracketed by an END IF around any job step to replace the COND= syntax.  Again, if the IF statement is true, the step is bypassed.

Q17.  What is the purpose of the PARM keyword in the EXEC statement?
A17.  The value after the PARM=  specifies control information to be passed to the executing program of the job step.

Q18.  What is the purpose and meaning of the REGION keyword and what JCL statement is it associated with?
A18.   REGION specifies the maximum CPU memory allocated for a particular job or job step.  If REGION is in the JOB card, it relates to the entire job;  if in the EXEC statement, it relates to the job step.

Q19. What is the purpose and meaning of the TIME keyword and what JCL statement is it associated with?
A19.  TIME specifies the maximum CPU time allocated for a particular job or job step.  If TIME is in the JOB card, it relates to the entire job;  if in the EXEC statement, it relates to the job step.

Q20.  What is the meaning of data definition name (ddname) and dataset name (dsname) in the DD statement?
A20.  Data definition name is the eight character designation after the // of the DD statement.  It matches the internal name specified in the steps executing program.  In COBOL that's the name specified after the ASSIGN in the SELECT ASSIGN statement. Dataset name is the operating system (MVS) name for the file.

Q21. How is the keyword DUMMY used in JCL?
A21.  For an output file DUMMY specifies that the output is to be discarded.  For input it specifies that the file is empty.

Q22. What does the keyword DCB mean and what are some of the keywords associated with it?
A22.  DCB stands for data control block; it is a keyword for the DD statement used to describe datasets. Keywords associated with it are BLKSIZE, DEN, LRECL and RECFM.

Q23. What is the difference between BLKSIZE and LRECL?
A23.  BLKSIZE specifies the number of bytes

IDMS Errorstatus or Errorcodes

IDMS error status codes are 4 characters. The first two are called major, the second two
are called minor.

MAJOR CODES

Code  Database Function

00    Any DML statement
01    FINISH
02    ERASE
03    FIND/OBTAIN
05    GET
06    KEEP
07    CONNECT
08    MODIFY
09    READY
11    DISCONNECT
12    STORE
14    BIND
15    ACCEPT
16    IF
17    RETURN
18    COMMIT
19    ROLLBACK
20    LRF Request

MINOR CODES

Code  Database Function Status

00    Combined with a major code of 00, this code indicates successful completion
      of the DML operation. Combined with a non-zero major code, this code
      indicates that the DML operation was not completed successfully, due to central
      version causes, such as time-outs and program checks.

01    An area has not been readied. When this code is combined with a major code
      of 16, an IF operation has resulted in a valid false condition.

02    Either the db-key used with a FIND/OBTAIN DB-KEY statement or the direct
      db-key suggested for a STORE is not within the page range for the specified
      record name.

04    The occurrence count of a variably occurring element has been specified as
      either less than zero or greater than the maximum number of occurrences
      defined in the control element.

05    The specified DML function would have violated a duplicates-not-allowed
      option for a CALC, sorted or index set.

06    No currency has been established for the named record, set or area.

07    Either the end of a set, area, or index has been reached or the set is empty.

08    Either the specified record, set, procedure, or LR verb is not in the
      subschema or the specified record is not a member of the set.

09    The area has been readied with an incorrect usage mode.

10    An existing access restriction or subschema usage prohibits execution of
      the specified DML specification. For the LRF users, the subschema in use
      allows access to database records only. For SPF users, this code may also
      indicate improper use of the ERASE statement. Commbined with a major code
      of 00, this code means the program has attempted to access a database
      record, but the subschema in use allows access to logical records only.

11    The record cannot be stored in the specified area due to insufficient space.

12    There is no db-key for the record to be stored. This is a system internal
      error and should be reported.

13    A current record of run unit has not been established or has been
      nullified by a previous ERASE statement.

14    The CONNECT statement cannot be executed because the requested record
      has been defined as a mandatory automatic member of the set.

15    The DISCONNECT statement cannot be executed because the requested record
      has been defined as a mandatory automatic member of the set.

16    The record cannot be connected to a set of which it is already a member.

18    The record has not been bound.

20    The current record is not the same type as the specified record name.

21    Not all areas being used have been readied in the correct usage mode.

22    The record name specified is not currently a member of the set name
      specified.

23    The area name specified is either not in the subschema or not an extent
      area; or the record name specified has not been defined within the area
      name specified.

25    No currency has been established for the named set.

26    Either no duplicates exist for the named record or the record name or
      SPF index entry cannot be found.

28    The run unit has attempted to ready an area that has been readied
      previously.

29    The run unit has attempted to place a lock on a record that is locked
      already by another run unit. A deadlock results and the run unit is
      aborted.

30    An attempt has been made to erase the owner record of a non-empty set.

31    The retrieval statement format conflicts with the record's location
      mode.

32    An attempt to retrieve a CALC/DUPLICATE record was unsuccessful; the
      value of the CALC field in variable storage is not equal to the value
      of the CALC control element in the current record of run unit.

33    At least on set in which the record participates has not been included
      in the subschema.

40    The WHERE clause in an OBTAIN NEXT logical-record request is inconsistent
      with a previous OBTAIN FIRST or OBTAIN NEXT command for the same record.
      Previously specified criteria, such as reference to a key field, has
      been changed. A path status of LR-ERROR is returned to the LRC block.

41    The subschema contains no path that matches the WHERE clause in a
      logical-record request. A path status of LR-ERROR is returned to the
      LRC block.

42    An ON clause included in the path by the DBA specified return of the
      LR-ERROR path status to the LRC block; an error has occurred while
      processing the LRF request.

43    A program check has been recognized during evaluation of a WHERE clause;
      the program check indicates that either a WHERE clause has specified
      comparison of a packed decimal field to an unpacked non-numeric data
      field, or data in variable storage or a database record does not conform
      to its description. A path status of LR-ERROR is returned to the
      LRC block unless the DBA has included an ON clause to override this action
      in the path.

44    The WHERE clause in a logical-record request does not supply a key
      element (sort key, CALC key or db-key) expected by the path. A path
      status of LR-ERROR is returned to the LRC block.

45    During evaluation of a WHERE clause, a program check has been recognized
      because a subscript value is neither greater than zero nor less than
      its maximum allowed value plus one. A path status of LR-ERROR is returned
      to the LRC block unless the DBA has included an ON clause to override this
      action in the path.

46    A program check has revealed an arithmetic exception (for example:
      overflow, underflow, significance, divide) during evaluation of a
      WHERE clause. A path status of LR-ERROR is returned to the LRC block
      unless the DBA has included an ON clause to override this action
      in the path.

53    The subschema definition of an indexed set does not match the indexed
      set's physical structure in the database.

54    Either the prefix length of an SR51 record is less than zero or the
      data length is less than or equal to zero.

55    An invalid length has been defined for a variable length record.

56    An insufficient amount of memory to accomodate the IDMS/R compression/
      decompression routines is available.

60    A record occurrence type is inconsistent with the set named in the
      ERROR-SET field in the IDMS communication block. This code usually
      indicates a broken chain.

61    No record can be found for an internal db-key. This code usually
      indicates a broken chain.

62    A system-generated db-key points to a record occurrence, but no
      record with that db-key can be found. This code usually indicates
      a broken chain.

63    The DBMS cannot interpret the DML function to be performed. When
      combined with a major code of 00, this means invalid function
      parameters have been passed on the call to the DBMS. For LRF users,
      a WHERE clause includes a keyword that is longer than the 32
      characters allowed.

64    The record cannot be found; the CALC control element has not been
      defined properly in the subschema.

65    The database page read was not the page requested.

66    The area specified is not avaiilable for update.

67    The subschema invoked does not match the subschema object tables.

68    The CICS interface was not started.

69    a BIND RUN-UNIT may not have been issued; the CV may be inactive
      or not accepting new run-units; or the connection with the CV may
      have been broken due to time-out or other factors. When combined
      with a major code of 00, this code means the program has been
      disconnected from the DBMS.

70    The database or journal file will not ready properly.

71    The page range for the area being readied or the page range
      requested cannot found in the DMCL.

72    There is insufficient memory to dynamically load a subschema or
      database procedure.

73    A CV run-unit will exceed the max. users value specified at system
      generation.

74    The dynamic load of a module has failed. If operating on the CV, a
      subschema or database procedure either was not found in the data
      dictionary or the load (core image) library or, if loaded, will
      exceed the number of subschema and the database procedures provided
      for at system generation.

75    A read error has occurred.

76    A write error has occurred.

77    The run-unit has not been bound or has been bound twice. When
      combined with a major code of 00, this code means either the program
      is no longer signed on to the subschema or the variable subschema
      tables have been overwritten.

78    An area wait deadlock has occurred.

79    The run-unit has requested more db-key locks than are available to
      the system.

80    The target node is either not active or has been disabled from the
      DDS configuration.

81    The database name specified is not known to the CV.

82    The subschema is not valid under the specified database.

83    An error has occurred in accessing native VSAM data sets.