Sybase Adaptive Server IQ 12.4.2, Руководство по администрированию и эксплуатации

Страница: 321 / 536

CHAPTER 8 Transactions and Versioning
301
Cannot perform DDL command now as a DDL command is already in progress.
If a
CREATE DBSPACE
or
DROP DBSPACE
command is in progress, and a user
explicitly issues a
CHECKPOINT
command, the checkpoint fails with the
message:
Run time SQL Error
If a
CHECKPOINT
command is in progress, a user who issues a
CREATE
DBSPACE
or
DROP DBSPACE
command gets the following message:
Cannot perform requested command as there is a
CHECKPOINT command in progress.
A user who issues
CREATE DBSPACE
during a drop gets the message
Cannot perform requested command as there is a
DROP DBSPACE command in progress.
A user who issues
DROP DBSPACE
during a create gets the message:
Cannot perform requested command as there is a
CREATE DBSPACE command in progress.
See “Versioning of temporary tables” for special rules regarding temporary
tables.
When one transaction issues a DDL command on a given table or index, any
other transaction that began before the DDL transaction commits, and that tries
to access that table, receives an error.
When this error occurs, any additional attempts to read or write to the table in
the current transaction will fail.
If a transaction modifies the definition of a table that is part of a join index, it
locks every table with any columns that are joined in that index. This result
occurs whether or not the particular columns in the original write transaction
are being joined.
Concurrency rules for
index creation
commands There is an exception to these rules for index creation commands.
CREATE
INDEX
and
CREATE JOIN INDEX
can occur concurrently with a
SELECT
on the
table(s) affected by the index creation. Adaptive Server IQ prevents use of the
new index or join index until the transaction creating the index commits.