Q1
What are the four divisions of a COBOL program?
- IDENTIFICATION DIVISION - Program identification (PROGRAM-ID)
- ENVIRONMENT DIVISION - Hardware/software environment, file assignments
- DATA DIVISION - Data definitions (FILE, WORKING-STORAGE, LINKAGE SECTION)
- PROCEDURE DIVISION - Executable code and business logic
Only IDENTIFICATION and PROCEDURE DIVISION are mandatory.
Q2
What is the difference between SECTION and PARAGRAPH in COBOL?
SECTION:
- Contains one or more paragraphs
- Ends with next SECTION or end of program
- Used for logical grouping
- Can be performed as a unit
PARAGRAPH:
- Basic unit of code
- Named block of statements
- Ends at next paragraph name or SECTION
PERFORM SECTION-NAME executes all paragraphs in the section.
PERFORM PARA-NAME executes only that paragraph.
Q3
What is a copybook and why is it used?
A copybook is a reusable code file that can be included in multiple programs using the COPY statement.
Uses:
- Standard record layouts
- Common working storage definitions
- Reusable paragraphs
- Ensures consistency across programs
Syntax:
COPY EMPREC. COPY EMPREC REPLACING ==EMP== BY ==WS-EMP==.
Benefits:
- Reduces code duplication
- Easier maintenance
- Standard definitions across team
Q4
What is SQLCODE and what are common values?
SQLCODE is a return code in SQLCA indicating the result of SQL execution.
Common SQLCODE values:
| 0 | Successful execution |
| 100 | No data found / End of cursor |
| -803 | Duplicate key on insert |
| -811 | Multiple rows returned for singleton SELECT |
| -904 | Unavailable resource |
| -911 | Deadlock/timeout |
| -922 | Authorization failure |
| -927 | DB2 not available |
Negative = Error, 0 = Success, 100 = No data
Q5
Explain the four divisions of a COBOL program.
IDENTIFICATION DIVISION: Program identification (PROGRAM-ID required). ENVIRONMENT DIVISION: Hardware/software configuration, file definitions. DATA DIVISION: Variable declarations, file records, working storage. PROCEDURE DIVISION: Executable code, business logic.
Q6
Explain COMP, COMP-1, COMP-2, and COMP-3 data types.
COMP: Binary (2/4/8 bytes based on PIC). COMP-1: Single precision floating point (4 bytes). COMP-2: Double precision floating point (8 bytes). COMP-3: Packed decimal (2 digits per byte + sign nibble).
Q7
How does SEARCH differ from SEARCH ALL?
SEARCH: Sequential search from current index position. SEARCH ALL: Binary search requiring sorted table with KEY clause. SEARCH ALL is faster for large tables but requires sorted data and indexed table.
Q8
What is COPY statement and how does REPLACING work?
COPY includes copybook at compile time. REPLACING substitutes text: COPY copybook REPLACING ==OLD== BY ==NEW==. Used for code reuse and standardization across programs.
Q9
Explain the PERFORM verb variations.
PERFORM para: Execute once. PERFORM para THRU para-exit: Execute range. PERFORM para n TIMES: Execute n times. PERFORM para UNTIL condition: Loop until true. PERFORM VARYING: Counter-controlled loop.
Q10
What is EVALUATE statement and its advantages?
EVALUATE is COBOL's case construct. EVALUATE TRUE WHEN condition-1 action WHEN OTHER default. Cleaner than nested IF, can evaluate multiple subjects, supports ALSO for multiple conditions, uses THRU for ranges.
Q11
What is INITIALIZE and what doesn't it initialize?
INITIALIZE sets fields to defaults: alphabetic to SPACES, numeric to ZEROS. Does NOT initialize: FILLER items, REDEFINES items, index data items. Can use REPLACING for custom values.
Q12
What is the purpose of LINKAGE SECTION?
LINKAGE SECTION defines parameters received from calling program. Items have no memory until CALL provides addresses. Used for passed parameters and dynamically addressed data.
Q13
What is GOBACK vs STOP RUN?
STOP RUN terminates entire run unit. GOBACK returns to caller; if main, acts like STOP RUN. Always use GOBACK in subprograms. STOP RUN from subprogram terminates everything.
Q14
Explain the difference between COND and IF/THEN/ELSE.
COND tests return codes to SKIP steps (negative logic). IF/THEN/ELSE tests conditions to EXECUTE steps (positive logic). IF supports complex expressions. COND on JOB affects all steps, on EXEC affects that step.
Q15
How does DISP parameter work?
DISP=(status,normal,abnormal). Status: NEW/OLD/SHR/MOD. Normal disposition after success. Abnormal after abend. Example: DISP=(NEW,CATLG,DELETE) creates, catalogs if OK, deletes if abend.
Q16
What does TYPRUN=SCAN do?
TYPRUN=SCAN validates JCL syntax without execution. No resources allocated, no programs run. Checks for errors before production submission.
Q17
Explain SPACE parameter options.
SPACE=(unit,(primary,secondary,directory)). Units: TRK/CYL/blocksize. Directory for PDS. Options: RLSE (release unused), CONTIG (contiguous), ROUND (round to cylinder).
Q18
What is DD DUMMY?
DD DUMMY discards output, provides EOF for input. No I/O actually performed. Equivalent: DSN=NULLFILE. Used for testing or optional files.
Q19
Explain REGION parameter.
REGION specifies memory limit. REGION=0M means system default (no limit). REGION=4M limits to 4MB. On JOB affects all steps, on EXEC affects that step.
Q20
What is DD * vs DD DATA?
DD * starts instream data ending with /*. DD DATA allows DLM=xx for custom delimiter when data contains /*. DD DATA,DLM=@@ ends with @@.
Q21
What is NOTIFY parameter?
NOTIFY=userid sends completion message. NOTIFY=&SYSUID notifies submitter. Multiple: NOTIFY=(user1,user2). Essential for batch monitoring.
Q22
How does IEFBR14 work?
IEFBR14 is null program (Branch Register 14 = return). Used for dataset management: create, delete, catalog. Example: //DEL EXEC PGM=IEFBR14 //DD DD DSN=file,DISP=(MOD,DELETE).
Q23
What is SQLCODE and common values?
SQLCODE indicates SQL result. 0=success, 100=not found/EOF, negative=error. Common: -803 duplicate key, -811 multiple rows, -904 unavailable, -911 deadlock, -818 timestamp mismatch.
Q24
Explain INNER JOIN vs LEFT OUTER JOIN.
INNER returns only matching rows. LEFT OUTER returns all left rows plus matching right (NULL if no match). LEFT preserves all left table rows.
Q25
How to handle NULL values?
NULL means unknown/missing. Use IS NULL/IS NOT NULL. COALESCE(col,default) substitutes. Indicator variables in COBOL detect NULL. NVL alternative function.
Q26
How does cursor work?
DECLARE defines cursor. OPEN executes SELECT. FETCH retrieves rows. CLOSE releases resources. FOR UPDATE allows positioned UPDATE/DELETE. WITH HOLD survives COMMIT.
Q27
What is indicator variable?
Indicator detects NULL. Declare: 01 VAR-IND PIC S9(4) COMP. Use: INTO :VAR:VAR-IND. Negative means NULL. Required for nullable columns.
Q28
How does COMMIT work?
COMMIT makes changes permanent, releases locks. ROLLBACK undoes changes. Implicit COMMIT at program end. Frequent COMMIT reduces lock duration.
Q29
What are KSDS, ESDS, RRDS, and LDS?
KSDS: Key sequenced, unique key, random/sequential access. ESDS: Entry sequenced, no key, RBA access. RRDS: Relative record, slot number access. LDS: Linear, byte stream.
Q30
What causes file status 23?
Record not found for READ/START/DELETE. Key doesn't exist. Verify key value, handle not-found condition in program logic.
Q31
Explain REPRO utility.
REPRO copies VSAM files. Can copy between VSAM and sequential. Options: FROMKEY/TOKEY, SKIP/COUNT, REPLACE. Used for backup, conversion.
Q32
How to handle file status 35?
File not found. Check: DSN spelling, catalog entry exists, file created. Add DD statement if missing.
Q33
Explain KSDS key definition.
KEYS(length offset). Length up to 255. Offset from position 0. Key extracted from record. Must be unique. Alphanumeric comparison.
Q34
What causes file status 22?
Duplicate key on WRITE. KSDS primary key must be unique. Check data, use REWRITE for updates instead.
Q35
What is pseudo-conversational programming?
Transaction ends after SEND, restarts on input. RETURN TRANSID(next) COMMAREA(data). Saves resources - no task waiting. Must restore state from COMMAREA.
Q36
Explain COMMAREA usage.
COMMAREA passes data between programs and transactions. Max 32KB. LINK/XCTL COMMAREA(data). Receiving program has DFHCOMMAREA in LINKAGE SECTION.
Q37
What is LINK vs XCTL?
LINK calls and returns to caller (like CALL). XCTL transfers permanently, no return. Use LINK for subroutines, XCTL for navigation.
Q38
What is BMS?
Basic Mapping Support handles screen I/O. DFHMSD defines mapset. SEND MAP displays. RECEIVE MAP gets input. Symbolic map in COBOL copybook.
Q39
Explain EIB fields.
EIB (Execute Interface Block): EIBCALEN=COMMAREA length, EIBTRNID=transaction, EIBAID=attention key, EIBRESP=response code. Available automatically.
Q40
How to debug CICS programs?
CEDF intercepts EXEC CICS. Step through commands, view/modify data. CEMT for resource status. Transaction dump for abends.
Q41
Explain REDEFINES clause with an example.
REDEFINES allows the same storage area to be referenced by different data names with different definitions.
Rules:
- Must be at same level as item being redefined
- Cannot redefine item with OCCURS
- Redefined item must appear first
- Lengths should match or redefining should be shorter
01 WS-DATE. 05 WS-DATE-NUM PIC 9(8). 01 WS-DATE-X REDEFINES WS-DATE. 05 WS-YEAR PIC 9(4). 05 WS-MONTH PIC 9(2). 05 WS-DAY PIC 9(2).
Same 8 bytes can be accessed as single number or individual components.
Q42
What is the difference between PARM and SYSIN for passing parameters?
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 /*
Q43
Explain the difference between INNER JOIN and LEFT OUTER JOIN.
INNER JOIN:
- Returns only matching rows from both tables
- If no match, row is excluded
LEFT OUTER JOIN:
- Returns all rows from left table
- Matching rows from right table
- NULL for right table if no match
-- INNER JOIN SELECT E.NAME, D.DEPT_NAME FROM EMPLOYEE E INNER JOIN DEPARTMENT D ON E.DEPT_ID = D.DEPT_ID; -- LEFT OUTER JOIN SELECT E.NAME, D.DEPT_NAME FROM EMPLOYEE E LEFT OUTER JOIN DEPARTMENT D ON E.DEPT_ID = D.DEPT_ID;
Use LEFT JOIN when you want all employees even those without department.
Q44
What is the purpose of COMMAREA in CICS?
COMMAREA (Communication Area) is used to pass data between programs or between transactions in pseudo-conversational programming.
Uses:
- Pass data between LINK/XCTL programs
- Save data between pseudo-conversational transactions
- Maximum size: 32KB
How it works:
- Calling program: COMMAREA option on LINK/XCTL/RETURN
- Called program: DFHCOMMAREA in LINKAGE SECTION
- Check EIBCALEN for length (0 = no COMMAREA)
* Calling program
EXEC CICS LINK
PROGRAM('SUBPROG')
COMMAREA(WS-DATA)
LENGTH(100)
END-EXEC.
* Called program
LINKAGE SECTION.
01 DFHCOMMAREA PIC X(100).
IF EIBCALEN > 0
MOVE DFHCOMMAREA TO WS-DATA
END-IF.
Q45
What is the difference between WORKING-STORAGE and LOCAL-STORAGE?
WORKING-STORAGE is allocated once at program load and persists across calls. LOCAL-STORAGE is allocated fresh each time the program is called and initialized each invocation. Use LOCAL-STORAGE for reentrant programs.
Q46
What is REDEFINES and what are its restrictions?
REDEFINES allows multiple data descriptions for same memory location. Restrictions: Cannot redefine with larger size, must be at same level, cannot use VALUE with REDEFINES target, occurs-depending cannot be redefined.
Q47
What is FILE STATUS and how to use it?
FILE STATUS is 2-byte field capturing I/O results. Declare in SELECT, check after each I/O. Common codes: 00=success, 10=EOF, 22=duplicate, 23=not found, 35=not exists, 39=mismatch.
Q48
How do you handle S0C7 abend?
S0C7 is data exception - non-numeric in numeric field. Debug: Check OFFSET in dump, review initialization, validate input data, check REDEFINES, examine hex dump for invalid bytes in COMP-3 fields.
Q49
Explain STRING and UNSTRING verbs.
STRING concatenates: STRING f1 DELIMITED BY SPACE f2 INTO output. UNSTRING splits: UNSTRING input DELIMITED BY ',' INTO f1 f2. POINTER tracks position, OVERFLOW handles errors, TALLYING counts fields.
Q50
What is OCCURS DEPENDING ON?
ODO creates variable-length tables. 05 TABLE OCCURS 1 TO 100 DEPENDING ON WS-COUNT. Table size varies based on counter. Used with variable-length records. Only variable portion at end of record.
Q51
Explain reference modification.
Reference modification extracts substring: WS-FIELD(start:length). Example: WS-NAME(1:3) gets first 3 chars. Start is 1-based. Length optional (to end). Works with MOVE, IF, DISPLAY.
Q52
What is CORRESPONDING option?
MOVE CORRESPONDING moves fields with matching names between groups. ADD CORRESPONDING/SUBTRACT CORRESPONDING for arithmetic. Convenient but use carefully - silent partial moves if names don't match exactly.
Q53
How does SORT work in COBOL?
SORT verb: SORT sort-file ON ASCENDING KEY key-field USING input-file GIVING output-file. INPUT/OUTPUT PROCEDURE allows processing during sort. RELEASE adds to sort, RETURN retrieves.
Q54
Explain CALL BY REFERENCE vs BY CONTENT vs BY VALUE.
BY REFERENCE: Passes address, changes visible to caller. BY CONTENT: Passes copy, original unchanged. BY VALUE: Passes value for C interop. Default is BY REFERENCE.
Q55
What is STEPLIB vs JOBLIB?
JOBLIB at job level provides libraries for all steps. STEPLIB at step level overrides JOBLIB for that step. Both searched before LINKLIST. Can concatenate multiple libraries.
Q56
Explain GDG (Generation Data Groups).
GDG maintains dataset versions. Define base with IDCAMS. Reference: (+1)=new, (0)=current, (-1)=previous. LIMIT controls kept generations. Useful for backup/archive strategies.
Q57
How to pass data between job steps?
DISP=PASS passes datasets between steps. Symbolic parameters carry values. GDG relative references. Temporary datasets (&&) auto-pass. JCL symbols set by SET statement.
Q58
What causes S0C7 in batch?
S0C7 is data exception - non-numeric in numeric field. Check: input file data, variable initialization, REDEFINES usage, field alignment. Find OFFSET in dump.
Q59
How does SORT utility work?
SORT FIELDS=(position,length,format,order). Input: SORTIN. Output: SORTOUT. Control: SYSIN. Options: INCLUDE/OMIT for filtering, OUTREC/INREC for reformatting.
Q60
What is IDCAMS and common commands?
IDCAMS manages VSAM and catalogs. Commands: DEFINE CLUSTER, DELETE, REPRO (copy), LISTCAT (list), ALTER, VERIFY, PRINT. IF/THEN/ELSE for conditional logic.
Q61
How to create and reference procedures?
PROC defines procedure, PEND ends it. Store in PROCLIB. Reference: EXEC procname or EXEC PROC=procname. Override: //procstep.ddname DD overrides.
Q62
Explain OUTPUT statement.
OUTPUT defines SYSOUT characteristics. //OUT1 OUTPUT CLASS=A,COPIES=2. Reference: SYSOUT=*,OUTPUT=*.OUT1. Centralizes output specifications.
Q63
What is SMS (Storage Management)?
SMS automates storage management. DATACLAS defines data attributes, STORCLAS controls placement, MGMTCLAS defines retention. ACS routines assign classes automatically.
Q64
What is JCLLIB ORDER?
JCLLIB ORDER specifies procedure library search order. Must be before first EXEC. Takes precedence over system proclibs.
Q65
Explain COND parameter logic.
COND skips step IF condition is TRUE. COND=(4,LT) skips if 4 < any prior RC. COND=(0,NE) skips unless all prior steps returned 0. Use IF for clarity.
Q66
What is EXPLAIN and how to use it?
EXPLAIN analyzes query access path. Results in PLAN_TABLE. Shows index usage, join method, sort operations. Review ACCESSTYPE, MATCHCOLS for tuning.
Q67
What causes -811 SQLCODE?
SELECT INTO returned multiple rows when expecting one. Solutions: Add WHERE for single row, use MAX/MIN, declare cursor for multiple rows.
Q68
Explain DB2 isolation levels.
UR: Uncommitted read (dirty read OK). CS: Cursor stability (current row locked). RS: Read stability (accessed rows locked). RR: Repeatable read (range locked, no phantom).
Q69
What is RUNSTATS and when to run it?
RUNSTATS collects statistics for optimizer. Run after significant data changes. Updates SYSTABLES, SYSINDEXES. Critical for optimal access path selection.
Q70
What is DB2 plan vs package?
Plan is bound executable SQL. Package is independent SQL unit. Modern approach: packages in collections with small plans. Packages allow separate rebind.
Q71
Explain -911 SQLCODE handling.
Deadlock or timeout. Two processes waiting for each other. Solutions: Retry transaction, consistent lock order, shorter transactions, appropriate isolation level.
Q72
What is REBIND and when needed?
REBIND updates access path without precompile. After RUNSTATS, index changes, performance issues. Can improve or degrade - test first.
Q73
Explain buffer pool importance.
Buffer pool caches data/index pages. Hit ratio critical. GETPAGE vs SYNCIO shows effectiveness. Size appropriately for workload.
Q74
Explain CI and CA in VSAM.
CI (Control Interval): I/O unit containing records and control info. CA (Control Area): Group of CIs. CI split on insert, CA split more expensive.
Q75
What is SHAREOPTIONS parameter?
SHAREOPTIONS(crossregion,crosssystem). 1=exclusive, 2=read share/write exclusive, 3=full sharing, 4=full sharing no refresh. Affects concurrent access.
Q76
How does alternate index work?
AIX provides secondary access path. DEFINE AIX, DEFINE PATH, BLDINDEX to build. UPGRADE maintains automatically. Access via PATH, not AIX directly.
Q77
What is FREESPACE parameter?
FREESPACE(CI%,CA%). CI% free for inserts within CI. CA% free for CI splits. More freespace reduces splits but uses space.
Q78
What is VERIFY utility?
VERIFY corrects catalog end-of-data after abend. Run before processing if previous job abended without proper CLOSE.
Q79
What is RBA?
RBA (Relative Byte Address) is byte offset from start. ESDS uses RBA for access. Changed by REORG. Use key for KSDS when possible.
Q80
How does BROWSE work?
STARTBR positions cursor. READNEXT/READPREV retrieves records. ENDBR ends browse. TOKEN for concurrent browses. Can use generic key.
Q81
What is file status 97?
VSAM OPEN error. Check: SHAREOPTIONS, file status, competing access, damaged cluster. Run VERIFY if needed.
Q82
Explain BUFND and BUFNI.
BUFND: data buffers. BUFNI: index buffers. More buffers improve performance but use memory. Tune based on access pattern.
Q83
How to handle CICS RESP codes?
EXEC CICS command RESP(ws-resp). Check DFHRESP(NORMAL) for success. RESP2 has additional info. Always check after commands.
Q84
What is START command?
START schedules future transaction. EXEC CICS START TRANSID(trans) INTERVAL(time) FROM(data). Used for background processing.
Q85
How does BROWSE work in CICS?
STARTBR positions, READNEXT/READPREV retrieves, ENDBR ends. TOKEN for concurrent browses. Use for sequential VSAM access.
Q86
What is temporary storage?
TS queue stores data across tasks. WRITEQ TS writes, READQ TS reads, DELETEQ removes. MAIN (memory) or AUXILIARY (disk).
Q87
Explain HANDLE CONDITION.
Sets error labels: HANDLE CONDITION NOTFND(para). Jumps on condition. Obsolete - prefer RESP option for cleaner handling.
Q88
What causes ASRA abend?
Program check (S0Cx) in CICS. Common: S0C7 data exception, S0C4 protection. Check CEDF, examine dump for cause.
Q89
What is CEDA?
CEDA defines resources online. CEDA DEFINE PROGRAM/TRANSACTION/FILE. CEDA INSTALL activates. RDO (Resource Definition Online).
Q90
Explain transient data.
TD queues for sequential I/O. Intrapartition: CICS internal. Extrapartition: external datasets. Defined in DCT. Trigger level for automatic transaction start.
Q91
What is SYNCPOINT?
SYNCPOINT commits changes. SYNCPOINT ROLLBACK undoes since last sync. Use for transaction consistency. Implicit at task end.
Q92
How do nested programs work in COBOL?
Nested programs are contained between IDENTIFICATION DIVISION and END PROGRAM. Can access outer program data with GLOBAL clause. COMMON attribute allows sibling access. Promotes modular design.
Q93
What is dynamic SQL?
SQL constructed at runtime. PREPARE creates executable. EXECUTE runs it. More flexible but less efficient. Security risk (injection).