JCL ⭐ Featured
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Q: What is the difference between PARM and SYSIN for passing parameters?

Answer:

PARM (EXEC statement):

  • Limited to 100 characters
  • Passed in memory to program
  • Accessed via LINKAGE SECTION
  • Good for small, simple parameters

SYSIN (DD statement):

  • No practical size limit
  • Read as a file by program
  • Can contain multiple records
  • Good for control cards, complex input
// PARM example
//STEP1 EXEC PGM=MYPROG,PARM='PARAM1,PARAM2'

// SYSIN example
//SYSIN DD *
CONTROL OPTION1
DATE=20231215
LIMIT=1000
/*
experienced interview
JCL ⭐ Featured
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Q: How to pass data between steps?

Answer:
Use DISP=PASS to pass datasets. Receiving step references same DSN. Or use symbolic parameters. GDG allows relative references (+1 created, 0 passed). Temporary datasets (&& prefix) auto-pass. SYSIN instream data copied to subsequent steps.
pass data steps
JCL ⭐ Featured
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Q: What is IEBGENER utility?

Answer:
IEBGENER copies sequential datasets. SYSUT1=input, SYSUT2=output, SYSIN=control. Simple copy needs only SYSUT1/SYSUT2/SYSIN DD DUMMY. Can reformat, generate, edit records with SYSIN statements. Being replaced by ICEGENER.
iebgener copy utility
JCL ⭐ Featured
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Q: Explain PARM parameter

Answer:
PARM passes data to program. EXEC PGM=PROG,PARM='value'. Max 100 characters. Program receives length prefix. PARM='abc,xyz' passes as one string. Program parses. Special chars need quotes. Alternative: SYSIN for larger data.
parm parameter program
JCL ⭐ Featured
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Q: What is SYSIN DD *?

Answer:
SYSIN DD * starts instream data. Data follows until /*. Program reads via SYSIN DD. Common for utility control statements. DD DATA,DLM=xx if data contains /*. SYSIN DD DUMMY for no input.
sysin instream input
DB2 ⭐ Featured
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Q: What is RUNSTATS and when to use it?

Answer:
RUNSTATS collects table/index statistics for optimizer. Run after significant data changes (loads, deletes). Updates catalog tables (SYSTABLES, SYSINDEXES). Optimizer uses for access path selection. RUNSTATS TABLESPACE db.ts INDEX(ALL).
runstats statistics optimizer
DB2 ⭐ Featured
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Q: What is DB2 catalog?

Answer:
Catalog tables describe DB2 objects. SYSIBM.SYSTABLES for tables, SYSIBM.SYSCOLUMNS for columns, SYSIBM.SYSINDEXES for indexes. Query catalog for metadata. Read-only except through DDL. Essential for documentation and analysis.
catalog sysibm metadata
JCL
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Q: How does IEBCOPY work?

Answer:
IEBCOPY copies/merges PDS members. SYSUT1=input PDS, SYSUT2=output PDS. SYSIN: COPY OUTDD=SYSUT2,INDD=SYSUT1 copies all. SELECT MEMBER=name for specific members. REPLACE option overwrites existing. Can compress PDS.
iebcopy pds utility
JCL
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Q: Explain DFSORT utility

Answer:
DFSORT sorts/merges files. SYSIN has SORT FIELDS=(1,10,CH,A). SORTIN=input, SORTOUT=output. Options: INCLUDE/OMIT for filtering, OUTREC/INREC for reformatting, SUM for summarization. ICETOOL provides extended functions.
dfsort sort utility
JCL
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Q: What is IDCAMS utility?

Answer:
IDCAMS manages VSAM and catalog. Commands: DEFINE CLUSTER, DELETE, REPRO, LISTCAT, ALTER, PRINT. //SYSIN DD * has commands. REPRO copies VSAM files. DEFINE creates VSAM clusters. IF/THEN/ELSE for conditional processing.
idcams vsam catalog