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Q: What is CTE (Common Table Expression)?
Answer:
CTE defines temporary result set. WITH cte_name AS (SELECT...) SELECT * FROM cte_name. Improves readability. Can be recursive for hierarchies. Multiple CTEs comma-separated. Referenced in main query. Scope is single statement.
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Q: What is the difference between KSDS and ESDS?
Answer:
KSDS (Key Sequenced Data Set):
- Records accessed by unique key
- Records stored in key sequence
- Has both data and index components
- Supports random and sequential access
- Can delete and reinsert records
- Most commonly used VSAM type
ESDS (Entry Sequenced Data Set):
- Records stored in arrival order
- Accessed by RBA (Relative Byte Address)
- No index component
- Cannot delete records (only mark inactive)
- Similar to sequential files
- Good for logs, audit trails
Use KSDS when: You need key-based access, updates, deletes
Use ESDS when: Sequential processing only, append-only data
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Q: What is 88-level condition name?
Answer:
88-level defines condition names for field values. 01 WS-STATUS PIC X. 88 VALID-STATUS VALUE 'Y'. 88 INVALID-STATUS VALUE 'N'. Use in IF: IF VALID-STATUS. Set using SET VALID-STATUS TO TRUE. Makes code self-documenting.
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Q: What is referential integrity?
Answer:
RI ensures foreign key values exist in parent. CREATE TABLE child ... REFERENCES parent(key). ON DELETE CASCADE/SET NULL/RESTRICT. DB2 enforces automatically. Constraint violations return -530/-531. Design carefully.
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Q: How to alter table structure?
Answer:
ALTER TABLE name ADD COLUMN col type. ALTER TABLE name DROP COLUMN col. ALTER TABLE name ALTER COLUMN col SET DATA TYPE. Some changes need REORG. Adding columns easy; changes may need unload/reload.
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Q: What is RRDS in VSAM?
Answer:
RRDS (Relative Record Dataset) accesses by relative record number (slot). Fixed length slots numbered 1, 2, 3... Can be empty slots. Good for direct access by position. Less common than KSDS/ESDS.
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Q: How to define KSDS cluster?
Answer:
IDCAMS DEFINE CLUSTER(NAME(ds.name) INDEXED KEYS(len offset) RECORDSIZE(avg max) SHAREOPTIONS(2 3)) DATA(NAME(ds.data) CYLINDERS(5 1)) INDEX(NAME(ds.index) CYLINDERS(1 1)). Keys required for INDEXED.
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Q: What causes file status 97?
Answer:
Status 97 indicates OPEN problem, often password or integrity. May be: dataset locked, open elsewhere without sharing, damaged dataset. Check SHAREOPTIONS, verify cluster status, recovery may be needed.
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Q: How to handle OCCURS INDEXED tables?
Answer:
Indexed tables use INDEXED BY: 05 TBL OCCURS 10 INDEXED BY IDX. SET IDX TO 1 initializes. SET IDX UP BY 1 increments. SEARCH uses index implicitly. More efficient than subscript-index conversion.
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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: What is KSDS key format?
Answer:
Keys defined by KEYS(length offset). Offset is 0-based. Key extracted from record at offset for length bytes. Alphanumeric comparison. Numeric keys need proper format. Key must be contiguous.
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Q: What is RBA?
Answer:
RBA (Relative Byte Address) is byte offset from dataset start. ESDS uses RBA for access. KSDS index points to RBA. Changed by REORG. Use key for KSDS, RBA only when necessary.
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Q: What is IMBED option?
Answer:
IMBED places sequence set (lowest index level) in data CA. Reduces I/O for index access. Uses more data space. Obsolete with modern systems - use defaults. May still see in old definitions.
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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: What is HURBA?
Answer:
HURBA (High Used RBA) marks end of data. Records beyond HURBA are unused space. LISTCAT shows HURBA. Grows as records added. REORG resets to eliminate gaps in ESDS.
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Q: What is ALTER statement?
Answer:
ALTER changes GO TO target dynamically. ALTER para-1 TO PROCEED TO para-2. Obsolete-causes maintenance nightmares. Makes flow unpredictable. Use EVALUATE or SET/IF instead. Some shops prohibit. Still legal but strongly discouraged.
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Q: How to use FUNCTION CURRENT-DATE?
Answer:
FUNCTION CURRENT-DATE returns 21-char timestamp. Format: YYYYMMDDHHMMSSDHHMM (D=hundredths, HH=GMT offset). MOVE FUNCTION CURRENT-DATE TO WS-TIMESTAMP. Parse components with reference modification or REDEFINES.
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Q: How to define FILE-CONTROL?
Answer:
SELECT file-name ASSIGN TO ddname. ORGANIZATION IS INDEXED. ACCESS MODE IS DYNAMIC. RECORD KEY IS key-field. ALTERNATE RECORD KEY IS alt-key. FILE STATUS IS ws-status. Maps COBOL file to physical dataset.
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Q: Explain BUFFERSPACE parameter
Answer:
BUFFERSPACE sets total buffer memory. Alternative to BUFND/BUFNI. BUFFERSPACE(65536) allocates 64K for buffers. System divides between index and data. Simpler than separate settings.
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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.
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Q: Explain DCB parameter
Answer:
DCB defines Data Control Block: RECFM (F/FB/V/VB/U), LRECL (record length), BLKSIZE (block size). DCB=(RECFM=FB,LRECL=80,BLKSIZE=27920). Can inherit from existing dataset. LRECL required for new datasets. BLKSIZE=0 lets system optimize.
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Q: How to define GDG in JCL?
Answer:
Create GDG base with IDCAMS DEFINE GDG. Reference generations: DSN=MY.GDG(+1) for new, DSN=MY.GDG(0) for current, DSN=MY.GDG(-1) for previous. DISP=(NEW,CATLG) for +1. Model DSCB needed for SMS-managed datasets.
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Q: What is symbolic parameter?
Answer:
Symbols are variables: SET symbol=value or &symbol on JOB/PROC. Reference: DSN=&HLQ..DATA. Resolved at job entry. EXEC proc,symbol=value overrides. SET statement defines. Symbols start with & and up to 8 characters.
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Q: What causes S0C7 in batch?
Answer:
S0C7 is data exception - non-numeric in numeric field. Check: input file data quality, initialize variables, correct REDEFINES, field alignment. Use OFFSET in dump to find statement. LE CEEDUMP shows data values. Common with new programs.
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Q: How to concatenate datasets?
Answer:
Stack DD statements: //INPUT DD DSN=FILE1,DISP=SHR // DD DSN=FILE2,DISP=SHR. No DD name on continuation. Read consecutively as one file. Different LRECL needs LRECL on first DD or DCB parameter. Concatenation limit varies by system.
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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: What is BMS?
Answer:
BMS (Basic Mapping Support) handles screen I/O. Map defines screen layout. DFHMSD macro creates mapset. SEND MAP displays screen. RECEIVE MAP gets input. Symbolic map in COBOL copybook. Physical map in load library.
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Q: How to use SET statement?
Answer:
SET symbol=value assigns value. SET DATE=&LYYMMDD (system symbol). Multiple: SET A=1,B=2. Scope: job/proc. Override on EXEC. SET can reference other symbols. Evaluated at conversion time. Enables parameter files.
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Q: What is PRTY parameter?
Answer:
PRTY sets selection priority. PRTY=15 on JOB card. Values 0-15 (15 highest). Affects when job selected from queue. JES2 processes higher PRTY first within class. Different from PERFORM (execution priority).
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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 BUFNO parameter
Answer:
BUFNO sets number of I/O buffers. DCB=(BUFNO=5). More buffers improve sequential performance but use memory. System default often 5. VSAM uses different buffering (BUFNI, BUFND). Too many can waste memory.
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Q: What is LENGTH in commands?
Answer:
LENGTH specifies data size. LENGTH(ws-len). Required for variable data. Set before RECEIVE. Check after READ for actual length. FLENGTH for fullword. Some commands have defaults.
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Q: What causes S0C4 in batch?
Answer:
S0C4 is protection exception - addressing unallocated memory. Causes: uninitialized pointer, subscript out of range, incorrect LINKAGE SECTION. Check CEEDUMP for offset. Likely program bug. Use debugger to trace.
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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: What is PATHDISP parameter?
Answer:
PATHDISP=(normal,abnormal) for USS files. Options: KEEP, DELETE. PATHDISP=(KEEP,DELETE). Used with PATH parameter. Similar to DISP for MVS datasets. Controls USS file retention.
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Q: How to code symbolic override?
Answer:
EXEC proc,SYM1=value1,SYM2=value2. Symbols defined in PROC with SET or & default. Override replaces default. Multiple overrides comma-separated. Must match PROC symbols. Case sensitive.
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Q: What causes INVALID DATA SET NAME?
Answer:
Dataset name violates rules: 44 char max, qualifier 8 max, start with letter/national, periods separate qualifiers, no double periods, no special characters. Check spelling, length, valid characters.
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Q: What is LRECL=X?
Answer:
LRECL=X means system-determined length. Usually for RECFM=U or special files. System calculates based on BLKSIZE or file characteristics. Not common for normal datasets. Used with certain utilities.
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Q: What is attribute byte?
Answer:
Attribute byte controls field display. In BMS: ATTRB=(PROT,BRT). Protected, unprotected. Bright, normal, dark. MDT (Modified Data Tag) for transmission. Set in map or program.
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Q: What is FRSET?
Answer:
FRSET (Field Reset) resets MDTs. EXEC CICS SEND MAP FRSET. Only changed fields transmitted back. Efficiency. Without FRSET, all unprotected transmitted. Use for repeat maps.
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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: 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 RLSE subparameter?
Answer:
RLSE releases unused space at close. SPACE=(CYL,(10,5),RLSE). Returns unused secondary allocations. Good practice for new datasets. Saves disk space. May cause allocation issues if reextended.
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Q: What is indicator variable?
Answer:
Indicator variable detects NULL values. Declare: 01 col-var. 01 col-ind PIC S9(4) COMP. Use: INTO :col-var:col-ind. If col-ind < 0, value is NULL. Set indicator negative to insert NULL. Required for nullable columns.
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Q: What is IMBEDDED index?
Answer:
IMBEDDED places sequence set in data CA. Reduces I/O for index access. Obsolete - modern systems don't benefit. Use system defaults. May see in old definitions.
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Q: What is maximum VSAM key length?
Answer:
Maximum key length is 255 bytes. KEYS(255 offset). Practical limits lower for performance. Index size grows with key. Keep keys reasonably sized.
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Q: How to handle CICS timeout?
Answer:
Set RTIMOUT on transaction. EXEC CICS HANDLE CONDITION ERROR. DTIMOUT for deadlock. Program design for cleanup. TIMEOUT condition raised.
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Q: Explain UPDATE with JOIN
Answer:
UPDATE table SET col = value FROM table t1 INNER JOIN table t2 ON... WHERE condition. Or: UPDATE t1 SET col = (SELECT col FROM t2 WHERE t2.key = t1.key). Merge statement is alternative.
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Q: What is FETCH FIRST?
Answer:
FETCH FIRST n ROWS ONLY limits result set. SELECT * FROM t ORDER BY col FETCH FIRST 10 ROWS ONLY. Optimizes query - doesn't retrieve all. OFFSET for paging. WITH TIES includes equal values.
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Q: What is DCLGEN?
Answer:
DCLGEN generates COBOL declarations from table. DCLGEN TABLE(name) LIBRARY(dataset) STRUCTURE(host-struct-name). Creates copybook with field definitions. Essential for maintaining table-program consistency.
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Q: Explain LOAD utility
Answer:
LOAD inserts large data volumes. LOAD DATA INTO TABLE name. Options: REPLACE, RESUME, LOG NO. Input is SYSREC dataset. LOAD faster than INSERT. Puts tablespace in COPY PENDING after LOG NO.
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Q: What is INITIALIZE and its options?
Answer:
INITIALIZE sets fields to default values: alphabetic to spaces, numeric to zeros. Options: REPLACING NUMERIC BY value, REPLACING ALPHANUMERIC BY value. Does not initialize FILLER or REDEFINES items. Useful for clearing record areas before processing.
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Q: How to define and use indexes?
Answer:
INDEX defined with OCCURS: 05 WS-TABLE OCCURS 10 INDEXED BY WS-IDX. SET WS-IDX TO 5 sets position. SET WS-IDX UP/DOWN BY 1 changes position. Use SEARCH verb with index. More efficient than subscripts for table access.
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Q: What is profile table?
Answer:
Profile tables store user-specific optimizer settings. DSN_PROFILE_TABLE, DSN_PROFILE_ATTRIBUTES. Override defaults for specific statements. Use QUERYNO correlation. Advanced tuning technique.
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Q: What is POINTER data type?
Answer:
USAGE POINTER stores memory addresses. SET ptr TO ADDRESS OF data. Used with SET ADDRESS OF linkage-item TO ptr. CALL with BY REFERENCE returns addresses. Supports dynamic memory and chained structures.
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Q: Explain condition-name SET TRUE
Answer:
SET condition-name TO TRUE assigns the condition's VALUE. If 88 ACTIVE VALUE 'A', SET ACTIVE TO TRUE moves 'A' to parent. Cleaner than MOVE 'A' TO STATUS. Makes code self-documenting. Multiple values take first.
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Q: What is CURSOR IS clause?
Answer:
In Screen Section, CURSOR IS field-name positions cursor. ACCEPT screen-name WITH CURSOR. Runtime positions to specified field. Can set dynamically. Used in interactive COBOL (CICS typically handles cursor differently).
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Q: What is TITLE statement?
Answer:
TITLE 'Page Header' sets listing page headers. Appears on each page of compilation listing. Useful for documentation. Multiple TITLES change as encountered. After IDENTIFICATION DIVISION start. Compiler directive, not executable.
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Q: What is LINEAR dataset?
Answer:
LINEAR VSAM is byte-addressable. No record structure. Used by DB2 tablespaces, system software. DEFINE CLUSTER LINEAR. Accessed via DIV (Data-in-Virtual) or memory mapping.
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Q: What is PROCEDURE-POINTER?
Answer:
USAGE PROCEDURE-POINTER stores program addresses. SET proc-ptr TO ENTRY 'PROGNAME'. CALL proc-ptr. Enables dynamic program selection. Similar to function pointers. Used in table-driven designs. Check ADDRESS OF for validity.
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Q: What is RETURN-CODE register?
Answer:
RETURN-CODE sets program completion status. MOVE 0 TO RETURN-CODE (success). MOVE 8 TO RETURN-CODE (warning). Passed to caller/JCL. Check RETURN-CODE after CALL. LE uses CEE3STS for detailed status.
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Q: How does DISP parameter work?
Answer:
DISP=(status,normal-end,abnormal-end). Status: NEW/OLD/SHR/MOD. Normal-end: DELETE/KEEP/PASS/CATLG/UNCATLG. Abnormal-end: same options. Example: DISP=(NEW,CATLG,DELETE) creates new, catalogs if OK, deletes if abend. MOD appends or creates if not exists.
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Q: What is CONTROLINTERVALSIZE?
Answer:
CONTROLINTERVALSIZE sets CI size explicitly. CONTROLINTERVALSIZE(4096). Powers of 2, max 32768. Let system default usually. Larger CI better sequential, worse random. Match to workload.
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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: How to define temporary dataset?
Answer:
Temporary datasets: DSN=&&TEMP or omit DSN. Exist for job duration only. Not cataloged. Passed between steps with DISP=PASS. Automatically deleted at job end. Example: //WORK DD DSN=&&TEMP,UNIT=SYSDA,SPACE=(CYL,5)
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Q: Explain SMS-managed storage
Answer:
SMS (Storage Management Subsystem) manages dataset placement. Specify STORCLAS, MGMTCLAS, DATACLAS in DD. DATACLAS sets DCB attributes, STORCLAS controls placement, MGMTCLAS defines retention. SMS uses ACS routines for assignment.
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Q: How to use IDCAMS conditionally?
Answer:
IF LASTCC/MAXCC condition THEN command. Example: IF MAXCC < 8 THEN REPRO... SET MAXCC/LASTCC resets codes. Allows conditional processing in IDCAMS job steps.
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Q: What is REPLICATE option?
Answer:
REPLICATE duplicates sequence set on each track. Each track has own copy of sequence set index. Reduces contention. Obsolete with modern systems. Uses more space.
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Q: What is IEFBR14?
Answer:
IEFBR14 is null program (Branch to Register 14 = return). Returns immediately. Used for dataset management: create, delete, catalog datasets. //DELETE EXEC PGM=IEFBR14 //DD DD DSN=name,DISP=(MOD,DELETE). Common for housekeeping.
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Q: How to use INCLUDE statement?
Answer:
INCLUDE MEMBER=name inserts JCL from JCLLIB member. Processed at conversion time. Can contain any JCL statements. Modular JCL design. INCLUDE can contain INCLUDE. SET statements affect included members.
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Q: What causes S913 abend?
Answer:
S913 is security violation. Not authorized to dataset or resource. Check: RACF/ACF2/TopSecret permissions, dataset profile, user authority level. S913-38 means insufficient access. Contact security administrator.
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Q: How to SEND MAP to terminal?
Answer:
EXEC CICS SEND MAP(mapname) MAPSET(mapsetname) FROM(symbolic-map) ERASE. CURSOR option positions cursor. FREEKB unlocks keyboard. ALARM sounds alarm. MAPONLY sends without data. DATAONLY sends only modified fields.
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Q: What is RECEIVE MAP?
Answer:
EXEC CICS RECEIVE MAP(name) MAPSET(mapset) INTO(symbolic-map). Gets terminal input. Modified fields only (MDT). Check EIBAID for key pressed. MAPFAIL if no data. Symbolic map populated with input.
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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: What causes NOTCAT error?
Answer:
NOTCAT means dataset not in catalog. Check: correct DSN spelling, dataset was cataloged, catalog searched is correct. Use DISP=SHR only for cataloged datasets. DISP=OLD with VOL=SER for uncataloged. LISTCAT verifies catalog entry.
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Q: What is GETMAIN?
Answer:
GETMAIN allocates temporary storage. EXEC CICS GETMAIN SET(pointer) LENGTH(size) INITIMG(X'00'). Returns pointer. Use for dynamic memory. FREEMAIN releases. SHARED for multi-task access. Automatic cleanup on task end.
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Q: Explain LIKE parameter
Answer:
LIKE copies DCB attributes from existing dataset. DCB=*.STEP1.DD or LIKE=catalog.dataset. Simplifies JCL. Model dataset must exist or be allocated earlier. Override specific attributes: DCB=(LIKE=...,LRECL=100).
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Q: What is transient data?
Answer:
TD queues for sequential I/O. EXEC CICS WRITEQ TD QUEUE(name) FROM(data). Intrapartition for CICS internal. Extrapartition for external datasets. Defined in DCT. Automatic trigger level option.
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Q: Explain HANDLE CONDITION
Answer:
HANDLE CONDITION sets error label. EXEC CICS HANDLE CONDITION NOTFND(para-notfnd). Jumps to label on condition. PUSH/POP HANDLE for nesting. Obsolete - prefer RESP option. Still seen in old code.
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Q: What is SET command?
Answer:
SET modifies resource state. EXEC CICS SET FILE(name) OPEN/CLOSED. SET TRANSACTION ENABLED/DISABLED. Requires authority. Dynamic resource management. Change status without CEDA.
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Q: What is KEYLEN parameter?
Answer:
KEYLEN specifies key length for new dataset. DCB parameter for VSAM-like. Or VSAM DEFINE CLUSTER KEYS(length offset). Length 1-255. Required for indexed organization. Offset from 0 or 1 depending on context.
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Q: How to handle multivolume datasets?
Answer:
VOL=(,,,n) allows n volumes. SPACE with volume count. SMS handles multivolume automatically. DISP=MOD extends to new volume. DATACLAS can specify multivolume. Large datasets need multivolume planning.
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Q: What causes S837 abend?
Answer:
S837 is end of volume and no more volumes available. Dataset needs more space. Solutions: allocate larger primary/secondary, increase volume count, extend dataset. IEFBR14 can extend with MOD DISP.
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Q: What is CEMT?
Answer:
CEMT inquires and sets resources. CEMT I TASK shows tasks. CEMT S FILE(name) OPEN opens file. Master terminal transaction. Operational control. I for inquire, S for set.
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Q: What is RETPD parameter?
Answer:
RETPD=nnn specifies retention days. Cannot delete until expired. EXPDT=yyddd for specific date. EXPDT=99365 or RETPD=9999 for permanent. Security software may override. Affects tape and disk datasets.
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Q: How to use JCLTEST?
Answer:
TYPRUN=JCLTEST validates JCL without execution. Checks syntax, dataset names, authorization. Some systems support TYPRUN=SCAN which is similar. Submit job and check messages. No resources actually allocated.
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Q: Explain EXPDT parameter?
Answer:
EXPDT=yyddd or EXPDT=yyyyddd expiration date. After this date, dataset can be deleted. EXPDT=99365 effectively permanent (1999 or 2099). RETPD alternative. Security software may enforce or override.
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Q: What causes NOT DEFINED TO CATALOG?
Answer:
Dataset exists on volume but not cataloged. Solutions: DISP=OLD,VOL=SER=volume, or catalog with IDCAMS DEFINE NONVSAM. Check correct catalog alias. May need ICF catalog update.
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Q: What causes IEF452I error?
Answer:
IEF452I is symbolic substitution error. Symbol not defined or wrong format. Check SET statements, PROC defaults. Verify symbol names match. May be missing &. Case matters for some systems.
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Q: How to set field attributes?
Answer:
Modify A field in symbolic map. DFHBMUNP=unprotected, DFHBMPRO=protected, DFHBMBRY=bright. Move to field-A before SEND. Dynamic attribute control.
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Q: What is EXPLAIN and how to use it?
Answer:
EXPLAIN analyzes query access path. EXPLAIN PLAN SET QUERYNO=1 FOR SELECT... Results in PLAN_TABLE. Shows index usage, join method, sort operations. Use for performance tuning. Review ACCESSTYPE, MATCHCOLS, PREFETCH columns.
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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: How to use DOCTEMPLATE?
Answer:
DOCTEMPLATE defines dynamic content. Create template with symbols. Insert data at runtime. EXEC CICS DOCUMENT SET/INSERT. For generating responses.
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Q: How to do paging with DB2?
Answer:
Use FETCH FIRST n ROWS ONLY with OFFSET or ROW_NUMBER(). Modern: SELECT * FROM (SELECT ROW_NUMBER() OVER(ORDER BY col) AS rn, t.* FROM table t) WHERE rn BETWEEN start AND end. Or cursor with FETCH FIRST.
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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 DEFINE ALTERNATEINDEX syntax?
Answer:
DEFINE AIX(NAME(aix.name) RELATE(base.cluster) KEYS(len offset)) DATA(NAME(aix.data)) INDEX(NAME(aix.index)). UNIQUEKEY or NONUNIQUEKEY. UPGRADE to maintain automatically. Must DEFINE PATH and BLDINDEX after.
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Q: How to use BLDINDEX utility?
Answer:
BLDINDEX creates AIX entries from base. IDCAMS BLDINDEX INDATASET(base) OUTDATASET(aix). Reads base cluster, writes AIX. Required after AIX definition. EXTERNALSORT for large datasets.
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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.