Q1
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.
Q2
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.
Q3
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.
Q4
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.
Q5
What is VERIFY utility?
VERIFY corrects catalog end-of-data after abend. Run before processing if previous job abended without proper CLOSE.
Q6
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.
Q7
How does BROWSE work?
STARTBR positions cursor. READNEXT/READPREV retrieves records. ENDBR ends browse. TOKEN for concurrent browses. Can use generic key.
Q8
What is file status 97?
VSAM OPEN error. Check: SHAREOPTIONS, file status, competing access, damaged cluster. Run VERIFY if needed.
Q9
Explain BUFND and BUFNI.
BUFND: data buffers. BUFNI: index buffers. More buffers improve performance but use memory. Tune based on access pattern.