Neoview SQL Reference Manual (R2.2)

Table 1-3 Concurrent DML and DDL Operations (continued)
DML Operations You Can Start
WaitsWaitsAllowedAllowed
1
REVOKE
Allowed
2
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 166).
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.
If the transaction isolation level is READ UNCOMMITTED, the default access mode is READ
ONLY. Further, for READ COMMITTED, you can specify only READ ONLY explicitly by using
the SET TRANSACTION statement.
READ ONLY transactions
• will not write anything into the transaction log
• will not abort if they extend beyond the system configured auto abort interval
• will not pin the transaction log
When AUTOCOMMIT is ON, the Neoview platform automatically uses READ ONLY transactions
for select statements. This could reduce concurrency if the select statement is long-running and
Transaction Management 35