RDF/IMP, IMPX, and ZLT System Management Manual

Network Transactions
HP NonStop RDF/IMP, IMPX, and ZLT System Management Manual—524388-002
13-12
Takeover and the RETAINCOUNT Value
elsewhere, the purger logs an RDF 823 event message identifying the particular
transaction.
Takeover and the RETAINCOUNT Value
In order for all systems in an RDF network to execute phase 3 takeover processing
correctly, you must ensure that all image data potentially needed for undo is available
on each system. The way to achieve that is to set the purger’s RETAINCOUNT to an
acceptable value on each system. For a complete discussion about this attribute and
how it works, refer to Section 10, Triple Contingency. (The same RETAINCOUNT
guidelines that apply to a triple contingency environment also apply to an RDF network
environment.)
Note that if you have not set the RETAINCOUNT properly and image files have been
purged that are subsequently needed for phase 3 takeover processing, the takeover
operations on the systems where the image data is missing might fail. In such a case,
your entire distributed database across all RDF backup systems could be
compromised with inconsistent data.
Network Configurations and Shared Access
NonStop SQL/MP DDL Operations
Under certain circumstances after a shared access NonStop SQL/MP DDL operation,
takeover network undo processing leads to an abort with database corruption.
To avoid this problem, use the following protocol when performing shared access
NonStop SQL/MP DDL operations in a network environment:
1. Issue the RDFCOM STOP RDF command on the primary system where you plan
to perform the shared access NonStop SQL/MP DDL operation.
2. From TMFCOM STATUS TRANSACTIONS, collect all the network transactions
that are currently in progress.
3. Wait until all transactions observed in step 2 have completed and are no longer
listed.
4. For all other primary nodes in your RDF network, run RDFCOM STATUS RDF
commands.
Note. If you have local transactions that do not touch data involved in network transaction
activity, and you do not want these local transactions undone just because data might be
missing for the network transactions during a takeover operation, you are advised to configure
separate RDF subsystems: one to protect just the data involved in network transaction activity,
and the second to protect the non-network data. Of course, both sets of data must have no
dependencies on the other.