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Table 1-3 Concurrent DML and DDL Operations (continued)
DDL Operations in
Progress
REVOKE
UPDATE
STATISTICS
1
DDL operation aborts the DML operation.
2
Allowed except during commit phase.
Table 1-4
describes the effect of various DDL and utility operations on table timestamps:
Table 1-4 Operations Effect on Table Timestamps
Alter Operation
ALTER TABLE
ALTER TRIGGER
CREATE CATALOG
CREATE INDEX
CREATE SCHEMA
CREATE TABLE
CREATE TRIGGER
CREATE VIEW
GRANT
POPULATE INDEX
PURGEDATA
REVOKE
UPDATE STATISTICS
Transaction Access Modes
A transaction has an access mode that is READ ONLY or READ WRITE. You can set the access
mode of a transaction by using a SET TRANSACTION statement. See
Statement" (page
READ ONLY
If a transaction is executing with the READ ONLY access mode, statements within the transaction
can read, but cannot insert, delete, or update, data in tables. This restriction means that among
the DML statements, only the SELECT statement can execute within that transaction. DDL
statements are not permitted in a READ ONLY transaction.
If the transaction isolation level is READ UNCOMMITTED, the default access mode is READ
ONLY. For READ COMMITTED, the default access mode is not READ ONLY, but you can
specify READ ONLY by using the SET TRANSACTION statement.
SELECT
UNCOMMITTED
1
Allowed
Allowed
Allowed
Allowed
188).
DML Operations You Can Start
SELECT SHARE
SELECT EXCLUSIVE
Waits
Allowed
Timestamp Updated
Yes, if you add columns or add or drop constraints No,
if you change attributes
No
No
Yes, if populated
No
No
Yes, of the table on which the trigger is defined
No
No
Yes
Yes
No
No
UPDATE/ INSERT
DELETE
Waits
2
Allowed
"SET TRANSACTION
Transaction Management
31
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