NonStop SQL/MP Reference Manual

NonStop SQL/MP Reference Manual—142115
C-63
Limits on Concurrent Utility and DML Operations
Limits on Concurrent Utility and DML Operations
Effect of VSBB on Concurrency
NonStop SQL/MP provides virtual sequential block buffering (VSBB) for read, update,
and insert operations. Although often more efficient than operations that do not use
VSBB, VSBB can cause increased lock waits and timeouts. In general, if you are
COLUMN HEADING X
RENAME X
Security attributes X
File attributes and whether you can alter them for tables (T) or
indexes (I) are as follows:
ALLOCATE T, I
AUDIT T
AUDITCOMPRESS T, I
BUFFERED T, I
LOCKLENGTH T, I
MAXEXTENTS T, I
RESETBROKEN T, I
SERIALWRITES T, I
TABLECODE T, I
VERIFIEDWRITES T, I
DML Operations
Utility Operations
SELECT
BROWSE
SELECT
SHARED
SELECT
EXCLUSIVE
DELETE/INSERT
UPDATE
COPY from a table
Without SHARE option A A A
1
N
With SHARE option A A A A
DUP a table A N N N
LOAD from a table
Without SHARE option A A A
1
N
With SHARE option A A A A
A Allowed
N Not allowed
1
Intermittent conflict can occur. If a SELECT locks a row for five minutes, the utility access to the row can
time out and abort the utility. Also, a SELECT attempting to access a row can abort if a utility locks the row for
longer than the SELECT time out.
ALTER Operation
Timestamp
Updated
Timestamp
Unaffected