SQL/MX 2.x Reference Manual (G06.24+, H06.03+)

Introduction
HP NonStop SQL/MX Reference Manual—523725-004
1-18
Concurrency
Table 1-5 lists concurrency limits on utilities.
Table 1-5. Concurrency Limits on Utility Operations (page 1 of 2)
Utility DML operations Other utilities
DDL
operations
Utilities that only read
metadata information:
EXPORTDDL
INFO
MXGNAMES
SHOWDDL
SHOWLABEL
VERIFY
All DML operations
(SELECT, UPDATE,
DELETE, INSERT) can be
performed concurrently.
Any utility in this
category can be
performed
concurrently.
Not
recommended.
Utilities that read both
metadata and user
data:
BACKUP
DUP (source table
only)
Only SELECT is allowed. Utilities that read
metadata can be
performed only
concurrently.
Not
recommended.
Utilities that read
metadata and update
user data:
IMPORT (not using
fast load)
All DML operations
(SELECT, UPDATE,
DELETE, INSERT) can be
performed concurrently.
If there are too many locks
on the partition, DP2
escalates to a table lock
which prevents concurrent
DML operations.
Utilities that read
metadata can
only be performed
concurrently.
Parallel imports
on the same table
are allowed.
Not
recommended.
Utilities that update
metadata and read
and write user data
offline:
MODIFY without
SHARED access*
POPULATE INDEX
Only SELECT is allowed.** Utilities that read
metadata can
only be performed
concurrently.
Not allowed.
Utilities that update
metadata and read
and potentially write
user data online:
MODIFY with
SHARED access
UPDATE STATISTICS
All DML operations are
allowed.
Utilities that read
metadata can
only be performed
concurrently.***
Not allowed.
* There are some exceptions. Dropping a partition from a hash partitioned table or index requires exclusive
access.
** The last phase of these operations requires exclusive access to the table or index, which prevents even
SELECT operations.
*** The last phase of the MODIFY operation requires exclusive access to the table or index, which prevents all
DDL and DML operations.