| Title: | DEC Rdb against the World |
| Moderator: | HERON::GODFRIND |
| Created: | Fri Jun 12 1987 |
| Last Modified: | Thu Feb 23 1995 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 1348 |
| Total number of notes: | 5438 |
Recently I was asked to talk to a technical expert from
Software, AG on some of the issues concerning running the
Adabas product on VAX/VMS in a Cluster and SMP environment.
These are some of the things I learned.
Adabas works in a VAXcluster environment but does not use the
distributed lock manager. One node would run the database
kernel, applications on other nodes would make network
connections to access it. Multiple kernels could be run but
they would not be accessing the same databases. You can set
up some stuff for failover. Transaction in progress may/may
not fail depending on where they were. The application would
be notified of incomplete transactions and would need to take
some action.
They are looking at possibly using the Distributed Lock
Manager but it would be for marketing reasons. They feel
that their performance is just fine without it, but so many
customers ask that they might do it. No commitments.
Adabas works just fine on an SMP machine but does not try to
take advantage of it (in version 2.1 anyway.) In a later
version (3.0?) they may use multi-threading so they would
actually use more than a singel processor. Note, application
code can run on multiple CPU's, but the kernel would only be
handled by one.
VMS shadowing (both controller and host based) is fully
supported. Since it is done down at the driver level they do
not see it or have to worry about it.
Terry Stowers
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 941.1 | Just a point of detail. | BAHTAT::DODD | gone to Helen's land | Thu Jun 20 1991 10:51 | 12 |
> take advantage of it (in version 2.1 anyway.) In a later
> version (3.0?) they may use multi-threading so they would
> actually use more than a singel processor. Note, application
Multi-threading would not allow use of more than one processor in an
SMP environment. You cannot have one thread executing on processor A
and one on processor B. You need multiple active images/processes to
gain from an SMP environment. You achieve this either with multiple
servers, or with child processes as in the PPL routines of VMS.
Andrew Dodd
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| 941.2 | SMP, clusters and bottlenecks | NOT003::DENTI | Ian Dent @NOT, Nottingham, UK | Fri Jun 21 1991 18:24 | 27 |
Adabas uses a product called Net-work to run in a cluster. It treats
a cluster as a DECnet network of nodes and uses DECnet for
communication between the nodes.
Adabas already uses multi-threading (up to 20 threads) within the
single server process. I believe that it is planned to allow multiple
server processes (maybe one per thread) in a future release. This
would allow the processes to be spread across many nodes in a cluster
or processors in a SMP machine.
Locking must be done between these multiple processess (using DLM?)
whereas, at present, all IO and hence locking, is handled by the
single process thereby avoiding any need for a VMS lock manager.
Whilst Adabas runs on an SMP machine without error there is likely
to be a bottleneck in a multi-CPU machine. In my experience,
Adabas/Natural Vaxes are CPU bound (rather than IO bound as for
most database systems) and typically one third of the CPU is taken
by the Adabas server. Therefore only 3 processors (1 for server,
2 for all the Natural users) can usefully be used (very dependant
on what application is doing).
Allowing multiple servers will reduce the performance of Adabas
but will remove bottlenecks of the limit in processors in a network
or an SMP machine that can be taken advantage of.
Ian
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