RDF/IMP and IMPX System Management Manual (RDF 1.3+)

Managing RDF
Compaq NonStop™ RDF/IMP and IMPX System Management Manual—522204-001
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RDF and SQL DDL Operations
(12:01). As soon as it encounters a commit or abort record whose timestamp is greater
than the specified timestamp, the updater will have processed all audit data for
transactions that committed or aborted up to the specified timestamp. Thus, the database
is in a completely consistent state with regard to transaction boundaries.
The updater keeps track of the first record it could not apply because its transaction
committed or aborted after the specified timestamp. In the above example, the updater’s
restart position in the image trail will be the first update record for t2. Thus, when
restarted, the updater will backtrack to that record. This practice ensures that no audit
data is lost during the STOP UPDATE to a timestamp operation.
If you erroneously set the timestamp too far into the future (for example, 26DEC2000),
the only way to correct this mistake is to enter a STOP RDF command, restart RDF, and
reenter the STOP UPDATE command with the correct timestamp.
See also the description of the STOP UPDATE
command in section 8.
RDF and SQL DDL Operations
When certain Data Definition Language (DDL) operations are performed on SQL/MP
tables protected by RDF, applications that depend on these operations are briefly denied
access to the database while the DDL operations are in progress. These periods of
unavailability, commonly called outages, end when the DDL operation completes.
When you perform SQL/MP DDL operations such as the following, you can either
include or omit the WITH SHARED ACCESS option:
•
The CREATE INDEX statement, used when creating an index on a table
•
The MOVE clause of the ALTER TABLE or ALTER INDEX statement, used when
moving, splitting, or merging disk file partitions, or when moving boundaries within
partitions
To determine all of the SQL/MP DDL operations that can be performed WITH
SHARED ACCESS, refer to the Compaq NonStop™ SQL/MP Reference Manual.
When included, the WITH SHARED ACCESS option specifies that the DDL operation
is to allow concurrent read-write Data Manipulation Language (DML) access and read-
only utility access to the objects on which it operates during all but the final phase of the
operation. For this reason, operations specifying the WITH SHARED ACCESS option
are sometimes referred to as Online DDL operations.
The only operations that must be performed WITH SHARED ACCESS are merge
partitions and move boundaries. It is recommended that you perform all other operations
with non-shared access.