HP OpenVMS System Manager's Manual, Volume 2:...

Managing DECdtm Services

Planning Transaction Logs

Creating Transaction Logs

Planning for a DECnet-PlusNetwork  

• Planning yourDECnet-Plus namespace



• Planning SCSNODE names inyour DECnet-Plus network

PlanningYour DECnet-Plus Namespace 

DECdtm does not support multiple DECnet-Plus namespaces.

This means that if you want to use software that uses DECdtmservices, you cannot use both a local namespace and a DECdns namespace.

PlanningSCSNODE Names in Your DECnet-Plus Network 

SCSNODE is a system parameter that defines the name of thecomputer. You must follow certain rules when choosing SCSNODE namesif you have a DECnet-Plus network and you want to perform DECdtm transactionsthat span either different OpenVMS Clusters or different standalonecomputers.

Rules for SCSNODE Names  

If you have a DECnet-Plus network and want to perform DECdtmtransactions that span different OpenVMS Clusters or different standalonecomputers, you must make sure that your SCSNODE names obey the followingrules:

• The SCSNODEname of each computer in a transaction group must be different from:

  TheSCSNODE names of the other computers in the transaction group; SCSNODEnames must be unique within a transaction group

  The DECnet simple names ofother computers on the same local root

  The DECnet synonyms of theother computers in the entire network

  For an explanation of transaction groups, see Understanding Transaction Groups



• If a computer is in an OpenVMSCluster, its SCSNODE name must also be different from:

  TheDECnet simple name of the other computers in the same cluster

  The DECnet simple names ofcomputers on the same local root as other cluster members

ACMS users, possibly Rdb users, and any other usersrunning a user-written application that calls DECdtm to participatein a distributed transaction with a remote system that has the HP DECnet-Plusfor OpenVMS network connection and whose nodes are connected usingonly an IP router might see the following error returned by DECnet: IPC-E-BCKTRNSFAIL, failure on the back translate address request This error is displayed upon a logical connection failurewhen DECnet-Plus cannot translate the remote node name. The errorcan be triggered when: TheDECnet-Plus node name for the remote system is not defined in thelocal DECnet-Plus database and is defined only as ALIAS in the TCP/IPname server for the remote node. For example, node XXYZZY might be defined as follows: 20.43.136.54 XXYZZY.ABC.DEF.COM, XXYZZY The node name cannot be resolvedfrom the DECnet database. In this case, the address resolution mechanismwill fall back on the TCP/IP database. If the node name is stillnot resolved, the service might fail with the error cited above. To avoid this situation, register the SCSNAME in theTCP/IP database.

UnderstandingTransaction Groups  

A transaction group is a group of computersinvolved in DECdtm transactions whose SCSNODE names must obey therules described in Rules for SCSNODE Names.

A transaction group conforms to the following guidelines:

• Each computerbelongs to no more than one transaction group.



• All the computers in an OpenVMSCluster belong to the same transaction group.



• If a single transaction spanscomputers A and B, then computers A and B belong to the same transaction group.

Transaction Group shows an exampleof a transaction group.  

Figure 2  Transaction Group

All nine computers shown in the figure are in the same transactiongroup because:

• A transaction spans a computer incluster FRED and a computer in cluster BILL. This means that the fourcomputers in cluster FRED and the four computers in cluster BILLare in the same transaction group.



• A transaction spans standalone computer TOM anda computer in cluster BILL. This means that the standalone computerTOM is in the same transaction group as the computers in clusterBILL.

Planning Transaction Logs

Creating Transaction Logs