RDF System Management Manual for H-Series RVUs (RDF 1.8)

Online Database Synchronization
With RDF/IMP, IMPX, or ZLT you can synchronize entire databases or selected volumes, files,
tables or even partitions while your applications continue to run. For information about this
capability, see Chapter 7 (page 155).
Online Dumps
With RDF/IMP, IMPX, or ZLT, all backup databases are audited by TMF. You can take online
dumps of a backup database at any time, thereby minimizing the amount of time necessary to
perform any subsequent takeover operation. For information about taking dumps while the
updaters are running, see Chapter 5 (page 121).
Subvolume-Level and File-Level Replication
By default, RDF provides volume-level protection, wherein changes to all audited files and tables
on each protected primary-system data volume are replicated to an associated backup-system
data volume.
RDF/IMP, IMPX, and ZLT also support subvolume-level and file-level replication. To use this
capability, you supply INCLUDE and EXCLUDE clauses when configuring updaters to identify
specific subvolumes and files you want either replicated or not replicated.
For information about subvolume-level and file-level replication, see Chapter 11 (page 261).
Shared Access DDL Operations
RDF includes two event messages (905 and 908) that assist you in the proper performance of
NonStop SQL/MP shared access DDL operations on the backup system. See “Performing Shared
Access DDL Operations” (page 142).
Fast Takeover
With RDF, RDF/MP, and RDF/MPX, an overall takeover operation can take a substantial amount
of time to complete because it entails all of the following:
1. Perform the actual RDF takeover (can take only a few seconds, plus the duration of the
level-4 Expand timer).
2. Turn on the audit flags of all data files in the backup database (can take seconds to minutes).
3. Take new online dumps of the backup database (can take hours). This step is recommended
but not required. Without dumps, however, the backup database cannot be recovered by
File Recovery, if necessary.
4. Start applications on the backup system and open all the data files (can take an hour or
more).
5. Reroute the communications lines for the front-end of the applications to the backup system.
With RDF/IMP and IMPX, because all of the data files on the backup system are audited, Step 2
is eliminated completely. Furthermore, you can perform Step 3 at any time, and the resultant
dumps are valid whenever the backup database becomes the database of record (such as after a
takeover or planned switchover). Additionally, for D46 and subsequent release environments,
it is possible to have your applications started on the backup system and in a “standby” mode
during normal RDF processing. For Enscribe files, the applications can actually have them open,
but cannot perform transaction activity against them.
With RDF/IMP and IMPX, therefore, it is now possible to achieve a complete takeover (or planned
switchover) literally within seconds.
60 Introducing RDF