Neoview SQL Reference Manual (R2.5)

Table 1-3 Concurrent DML and DDL Operations (continued)

DML Operations You Can Start

UPDATE/ INSERT

DELETE

SELECT EXCLUSIVESELECT SHARESELECT

UNCOMMITTED

DDL Operations in

Progress

WaitsWaitsAllowedAllowed

REVOKE

Allowed

AllowedAllowedAllowedUPDATE

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

Timestamp UpdatedAlter Operation

Yes, if you add columns or add or drop constraints No,

if you change attributes

ALTER TABLE

NoALTER TRIGGER

NoCREATE CATALOG

Yes, if populatedCREATE INDEX

NoCREATE SCHEMA

NoCREATE TABLE

Yes, of the table on which the trigger is definedCREATE TRIGGER

NoCREATE VIEW

NoGRANT

YesPOPULATE INDEX

YesPURGEDATA

NoREVOKE

NoUPDATE 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 “SET TRANSACTION

Statement” (page 188).

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.

Transaction Management 31