Q1
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.
Q2
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.
Q3
Explain REPRO utility.
REPRO copies VSAM files. Can copy between VSAM and sequential. Options: FROMKEY/TOKEY, SKIP/COUNT, REPLACE. Used for backup, conversion.
Q4
How to handle file status 35?
File not found. Check: DSN spelling, catalog entry exists, file created. Add DD statement if missing.
Q5
Explain KSDS key definition.
KEYS(length offset). Length up to 255. Offset from position 0. Key extracted from record. Must be unique. Alphanumeric comparison.
Q6
What causes file status 22?
Duplicate key on WRITE. KSDS primary key must be unique. Check data, use REWRITE for updates instead.
Q7
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.
Q8
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.
Q9
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.
Q10
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.
Q11
What is VERIFY utility?
VERIFY corrects catalog end-of-data after abend. Run before processing if previous job abended without proper CLOSE.
Q12
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.
Q13
How does BROWSE work?
STARTBR positions cursor. READNEXT/READPREV retrieves records. ENDBR ends browse. TOKEN for concurrent browses. Can use generic key.
Q14
What is file status 97?
VSAM OPEN error. Check: SHAREOPTIONS, file status, competing access, damaged cluster. Run VERIFY if needed.
Q15
Explain BUFND and BUFNI.
BUFND: data buffers. BUFNI: index buffers. More buffers improve performance but use memory. Tune based on access pattern.