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Q: What is UNLOAD utility?
Answer:
UNLOAD extracts data to sequential file. UNLOAD FROM TABLE name. Output format matches LOAD input. Used for data migration, backup, extract. Can include WHERE clause for filtering.
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Q: How to tune DB2 queries?
Answer:
Check EXPLAIN output. Look at: access type (index vs scan), join method, sort operations. Add indexes for predicates. Rewrite with hints. Update statistics. Check for full tablespace scans. Monitor actual execution.
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Q: Explain STRING and UNSTRING operations
Answer:
STRING concatenates multiple fields into one: STRING field-1 DELIMITED BY SPACE field-2 INTO output-field. UNSTRING splits one field into multiple: UNSTRING input-field DELIMITED BY ',' INTO field-1 field-2. Both support POINTER for position tracking and OVERFLOW handling.
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Q: What is MOVE CORRESPONDING?
Answer:
MOVE CORRESPONDING moves all fields with matching names between groups. MOVE CORR INPUT-REC TO OUTPUT-REC. Only moves if names match exactly. Moves all matches, not just first. Useful for record transformations. Debug carefully-silent partial moves.
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Q: How to use EXPLAIN tables?
Answer:
PLAN_TABLE primary output. DSN_STATEMNT_TABLE for cost. DSN_FUNCTION_TABLE for functions. INSERT EXPLAIN before statement. Query tables after. PLANNO, ACCESSTYPE, MATCHCOLS important columns.
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Q: Explain REUSE parameter
Answer:
REUSE allows reloading without delete/define. DEFINE CLUSTER ... REUSE. OPEN OUTPUT resets to empty. Like scratch and rewrite. Good for temporary work files. Cannot be UNIQUE.
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Q: How to use STRING with POINTER?
Answer:
STRING uses POINTER to track position: STRING field-1 DELIMITED SIZE INTO output WITH POINTER pos-var. Pointer shows next available position. Initialize before first STRING. Check for overflow. Continue STRING in multiple statements.
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Q: What is READY TRACE?
Answer:
READY TRACE turns on paragraph tracing. Shows paragraph names as executed. RESET TRACE turns off. Must compile with debugging option. Output goes to SYSOUT. Replaced by better debuggers but useful for quick flow analysis.
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Q: How to list VSAM catalog entries?
Answer:
LISTCAT ENTRIES(ds.pattern) ALL. Shows cluster info: space, attributes, records. LISTCAT LEVEL(high.level) for multiple. Output to SYSPRINT. Essential for troubleshooting.
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Q: What is XML GENERATE?
Answer:
XML GENERATE creates XML from data. XML GENERATE output FROM data-item. Optional: COUNT IN length, WITH ENCODING, WITH XML-DECLARATION. Generates element for each field. Names from data names. COBOL 5+ feature.
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Q: What is EXAMINE utility?
Answer:
EXAMINE checks VSAM structural integrity. EXAMINE NAME(ds.name) INDEXTEST DATATEST. Finds problems in index, data. Run periodically or when problems suspected. Output shows errors.
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Q: How does OUTPUT statement work?
Answer:
OUTPUT defines SYSOUT processing options. //OUT1 OUTPUT CLASS=A,DEST=LOCAL,COPIES=2. Reference: //SYSOUT DD SYSOUT=*,OUTPUT=*.OUT1. Centralizes output attributes. Can specify JESDS for JES-level control. Forms, burst options available.
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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.
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Q: How to diagnose VSAM problems?
Answer:
Check file status first. LISTCAT for definition. EXAMINE for structure. IDCAMS PRINT to see data. System messages in JES output. VERIFY after abnormal end. Statistics from catalog.
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Q: How to check job status?
Answer:
SDSF DA/ST panels show jobs. TSO STATUS command. JES2 J'jobname'. JESMSGLG shows JCL, allocation. JESYSMSG has error details. Return code in JESMSGLG. Condition codes per step. Check SYSOUT for program output.
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Q: What causes S722 abend?
Answer:
S722 is output limit exceeded. Too many lines to SYSOUT. Check program loops causing excessive output. Increase output limit in installation parameters. Or reduce output volume. May need job card BYTES parameter.
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Q: What is JESDS parameter?
Answer:
JESDS specifies JES dataset for OUTPUT. JESDS=ALL creates JESMSGLG, JESJCL, JESYSMSG. JESDS=LOG for JESMSGLG only. On OUTPUT statement. Controls system output generation. Used for output management.
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Q: Explain NULLFILE keyword?
Answer:
NULLFILE is alternate for DUMMY. //DD DD NULLFILE. Discards output, provides EOF for input. DSN=NULLFILE equivalent. No actual dataset. Useful for testing without actual files.
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Q: How to reference PDS member?
Answer:
DSN=PDS.NAME(MEMBER). Direct member reference. DISP must allow access. For input, member must exist. For output, overwrites or creates. IEBCOPY for multiple members. Member name 1-8 characters.
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Q: What is SEGMENT parameter?
Answer:
SEGMENT limits output lines per dataset. On OUTPUT statement. SEGMENT=nnn pages per segment. JES creates multiple output datasets. Helps with huge print files. Easier to handle smaller pieces.
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Q: How to use ACCUM option?
Answer:
ACCUM accumulates map output. EXEC CICS SEND MAP ACCUM. Build complete screen before send. Final EXEC CICS SEND PAGE. For multi-map screens. Message building.
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Q: Explain symbolic map structure
Answer:
Symbolic map copybook. Field name with L (length), F (flag), A (attribute), I (input), O (output). Set -1 in length for cursor. Check flag for modified. Program data area.
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Q: What is OVERFLOW condition?
Answer:
OVERFLOW when output exceeds page. During SEND with paging. Handle to manage paging. RESP check. Terminal specific limits. May need to restructure output.
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Q: What is SORT and MERGE in COBOL?
Answer:
SORT orders records: SORT SORT-FILE ON ASCENDING KEY-FIELD USING INPUT-FILE GIVING OUTPUT-FILE. INPUT/OUTPUT PROCEDURE allows processing during sort. MERGE combines pre-sorted files: MERGE SORT-FILE ON KEY USING FILE-1 FILE-2 GIVING OUTPUT-FILE.
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Q: How to work with OCCURS indexed tables?
Answer:
Define: 01 WS-TABLE. 05 WS-ENTRY OCCURS 100 INDEXED BY WS-IDX. 10 WS-NAME PIC X(20). 10 WS-VALUE PIC 9(5). Access: MOVE WS-NAME(WS-IDX) TO output. Search: SEARCH WS-ENTRY WHEN WS-NAME(WS-IDX) = 'VALUE' perform action.
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Q: What is OPEN mode options?
Answer:
OPEN INPUT for read, OUTPUT for write (creates), I-O for read/update, EXTEND for append. Multiple files per OPEN. OPEN OUTPUT deletes existing file! EXTEND preserves and adds. File must be closed before reopening in different mode.
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Q: What is APPLY WRITE-ONLY?
Answer:
APPLY WRITE-ONLY FOR file-name optimizes output buffer handling. System doesn't preserve record area after WRITE. Can't re-read just-written record. Improves I/O performance. Use when write-only access pattern is guaranteed.
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Q: Explain IDCAMS PRINT utility
Answer:
PRINT displays VSAM contents. PRINT INFILE(dd) CHARACTER/HEX/DUMP. FROMKEY/TOKEY limits range. COUNT limits records. Useful for debugging, verification. Output to SYSPRINT.
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Q: Explain JSON GENERATE
Answer:
JSON GENERATE creates JSON from data. JSON GENERATE output FROM data-item. NAME clause for custom keys. SUPPRESS clause omits fields. COUNT IN length. COBOL V6+ feature. Generates name-value pairs from structure.
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Q: How to switch file for restart?
Answer:
IDCAMS DELETE/DEFINE or REUSE attribute. REUSE allows OPEN OUTPUT reset. Alternative: JCL with DISP=(NEW,CATLG,DELETE) pattern. Checkpoints may need restart considerations.
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Q: Explain DD DUMMY statement
Answer:
DD DUMMY discards output/provides EOF for input. No I/O actually performed. DUMMY, DSN=NULLFILE equivalent. Use to skip optional outputs or provide empty input. Program sees immediate EOF on read. Writes succeed but discarded.
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Q: What is MSGLEVEL parameter?
Answer:
MSGLEVEL=(statements,messages). Statements: 0=JOB only, 1=all JCL, 2=input JCL. Messages: 0=completion only, 1=all including allocation. MSGLEVEL=(1,1) shows everything. MSGLEVEL=(0,0) minimal output. Affects JESMSGLG.
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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.
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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.
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Q: Explain JES2 control cards
Answer:
JES2 cards start with /*. /*JOBPARM limits resources. /*ROUTE sends output. /*OUTPUT JESDS specifies JES output. /*PRIORITY sets priority. Process by JES2, not passed to job. Position after JOB card before first EXEC.
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Q: Explain DD SYSOUT statement
Answer:
SYSOUT=class routes output to JES spool. SYSOUT=* uses MSGCLASS from JOB. SYSOUT=A specific class. Additional: COPIES=2, DEST=node.userid, FCB=fcb-name. Held output: HOLD=YES. OUTPUT statement for complex options.
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Q: What is INTRDR?
Answer:
SYSOUT=(class,INTRDR) submits output as new job. Internal reader. Programs can submit jobs dynamically. Class often B. Output must be valid JCL. Used for job scheduling, dynamic workflows.
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Q: How does MERGE work?
Answer:
DFSORT MERGE combines pre-sorted files. SORTIN01, SORTIN02, etc. inputs. MERGE FIELDS=(1,10,CH,A). Files must be sorted on merge key. Output one sorted file. Preserves input order for equal keys.
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Q: What is CNTL statement?
Answer:
CNTL groups control statements. //name CNTL establishes scope. //name ENDCNTL ends it. Used with OUTPUT or other complex statements. Provides modularity. Can be referenced by name from multiple DDs.
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Q: What is SPIN parameter?
Answer:
SPIN=UNALLOC releases output immediately on step/job end. SPIN=(UNALLOC,step) at step end. Without SPIN, output held until job completes. Allows viewing long job output early. On DD SYSOUT statement.
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Q: Explain DEST parameter?
Answer:
DEST routes output. DEST=nodeid.userid sends to remote. DEST=LOCAL for local printer. On OUTPUT statement or SYSOUT. JESDS respects DEST. Can be printer name or user. Network delivery support.
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Q: What is PAGING option?
Answer:
PAGING breaks large output. EXEC CICS SEND MAP PAGING. User navigates pages. Autopaging available. Terminal paging commands. For long reports on screen.
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Q: How to use MODIFY parameter?
Answer:
MODIFY references FCB image. MODIFY=(fcb,trc) on OUTPUT. FCB controls forms. TRC is table reference character. For print formatting. Installation-defined FCBs. Used with special forms.
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Q: What is DOCUMENT?
Answer:
DOCUMENT builds dynamic content. CREATE, SET, INSERT commands. For web responses. Template-based output. Modern CICS web support. Replace BMS for web.
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Q: What is SPUFI?
Answer:
SPUFI (SQL Processing Using File Input) is TSO tool for interactive SQL. Input dataset with SQL statements. Output shows results. Good for testing queries, DDL, quick data checks. Not for production processing.
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Q: What is REUSE option purpose?
Answer:
REUSE allows OPEN OUTPUT to reset file. Like delete/define without overhead. Good for work files. DEFINE CLUSTER ... REUSE. Cannot be UNIQUE. Efficient for scratch files.
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Q: What is EXEC CICS SPOOLOPEN?
Answer:
SPOOLOPEN accesses JES spool. SPOOLREAD/SPOOLWRITE for data. SPOOLCLOSE ends. Process job output. Modern batch integration. Requires authorization.