👁 0
Q: When should I use COMMIT in DB2?
Answer:
COMMIT saves all changes since the last COMMIT and releases locks.
When to COMMIT:
- After processing a logical unit of work
- Periodically in long-running batch (every N records)
- Before ending the program successfully
Frequency Guidelines:
- Too frequent: Performance overhead
- Too rare: Lock contention, large log
- Typical: Every 100-1000 records in batch
Best Practice:
MOVE 0 TO WS-COMMIT-COUNT.
PERFORM PROCESS-RECORD.
ADD 1 TO WS-COMMIT-COUNT.
IF WS-COMMIT-COUNT >= 500
EXEC SQL COMMIT END-EXEC
MOVE 0 TO WS-COMMIT-COUNT
END-IF.
Note: In CICS, syncpoint (COMMIT) happens automatically at task end. Explicit SYNCPOINT is rarely needed.
👁 0
Q: What is the difference between SECTION and PARAGRAPH in COBOL?
Answer:
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.
👁 0
Q: What is CI and CA in VSAM?
Answer:
CI (Control Interval) is I/O unit, like block. Contains records, free space, control info. CA (Control Area) is group of CIs. CISIZE affects performance. CI split when full. CA split more expensive.
👁 0
Q: Explain SPACE parameter options
Answer:
SPACE=(unit,(primary,secondary,directory)). Unit: TRK/CYL/block-size. Primary allocated first, secondary in 15 increments. Directory only for PDS. RLSE releases unused. CONTIG requires contiguous. Example: SPACE=(CYL,(10,5,20),RLSE)
👁 0
Q: Explain CICS task and transaction
Answer:
Transaction is unit of work started by TRANSID. Task is CICS execution instance. One transaction may create multiple tasks. Task has TCA (Task Control Area). EIBTRNID has transaction ID. Concurrent tasks share resources.
👁 0
Q: Explain AVGREC parameter
Answer:
AVGREC specifies space in record units. AVGREC=U (units), K (thousands), M (millions). SPACE=(80,(100,10),,,ROUND) with AVGREC=K means 100,000 records. Easier than calculating tracks. System converts to tracks.
👁 0
Q: How to force uncataloged?
Answer:
VOL=SER=volume forces uncataloged access. DISP=(OLD,KEEP). System searches specified volume, not catalog. UNIT required. Bypasses catalog entirely. Useful for specific volume access. Security still applies.
👁 0
Q: How to allocate SYSDA?
Answer:
UNIT=SYSDA for disk. Generic device group. Installation defines SYSDA contents. Usually includes all available disk. SMS may direct allocation. UNIT=3390 for specific device type. SYSDA preferred for portability.
👁 0
Q: What is a DB2 plan vs package?
Answer:
Plan is executable form of program's SQL, bound from DBRM. Package is independent unit, can be shared. Plans contain packages or direct SQL. Packages allow separate rebind. Modern approach: package collections with small plans.
👁 0
Q: How to handle SMS conversion?
Answer:
SMS manages storage automatically. Migrate VSAM to SMS: DATACLAS, STORCLAS, MGMTCLAS. ACS routines for assignment. Remove explicit VOL/UNIT. Benefits: automation, management.
👁 0
Q: What is GOBACK vs STOP RUN?
Answer:
STOP RUN terminates entire run unit (all programs). GOBACK returns to caller; if main program, acts like STOP RUN. Use GOBACK in subprograms to return control. STOP RUN from subprogram ends everything unexpectedly.
👁 0
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)
👁 0
Q: What is UNIT parameter?
Answer:
UNIT specifies device type. UNIT=SYSDA (direct access), UNIT=TAPE, UNIT=3390. UNIT=AFF=ddname shares device. UNIT=(SYSDA,2) allocates 2 volumes. SMS may override. UNIT=VIO for virtual I/O (memory only).
👁 0
Q: Explain RETURN command
Answer:
RETURN ends program or task. EXEC CICS RETURN returns to caller. EXEC CICS RETURN TRANSID(next) COMMAREA(data) for pseudo-conv. IMMEDIATE for no COMMAREA. End of logical unit.