We have a main and a backup server (HPUX11), sharing a disk-array containing the chunks (raw devices) of the Informix 7.3 runnig on the main server.
If the main server crashes (or is down for maintenance) I want to start an informix on the backup machine using the same chunk files that are normally used by the main server. (the device file names for the chunk files will be identical, the hardware paths won´t be).
Assuming that the dbspace containing this chunk is not critical, doenot contain logs, and is not rootdbs, whenyou create the dbspace on backup server give this chunk as the chunk name (link) and continue as usual, I hope this will work. I have done something similar, chunk being shared by 2 informixserver residing on the same m/c and the chunk was a cooked file.
That sounds quite good.
actually I wanted to go a bit further:
I simply wanted to use the same onconfig file on both machine. The ROOTPATH points to the 1st chunk of the rootdbs.
Everything else should be configured in there.
The spaces will also contain logical logs.
The spaces will be raw devices.
I don't think that is possible i.e. using the same ROOTDBS by 2 different informix server. This is because the rootdbs contains the critical data and moreover you are placing the logs in rootdbs. Whenever we try to bring up the Informix server, it reads from a file called $INFORMIXDIR/etc/oncfg_<DBSERVER Name>.<DBSERVER Number> which contains the logical log details, checkpoints details and these will be different for 2 different servers. Even if you start (from scratch) with same config. this files will contain different information for 2 different servers.
I have another config. I'm working with Veritas Volume Manager(VVM), think you have to work with something similar to create Volumes for the chunks. With VVM you can export and import Volumegroups, even with a force option, when one server crashes. But using links is ok too.
You only have to copy once the INFORMIXDIR and when any change is made, do it on both. And take care of starting up both server ;-(
thanks for the info. We are using the LVM (logical volume manager) that comes with HPUX.
I am not sure wether we are talking about the same thing. I want to access the chunks alternatively, only one informix up at one time.
I could not find any $INFORMIXDIR/etc/oncfg_<DBSERVER Name>.<DBSERVER Number> (I think this Informix 9.x?). I only have the "normal" onconfig file. Of course as a Christian said, the onconfig (and the rest of the installation) must be identical on both installations.
Unfortunnately I cannot test that stuff at the moment, but I´ll post it here when I know
it went fine. After stopping the SERVERA and starting SERVERB
we importerted the volume groups from the Raid an set them to active.
Then we had to alter the onconfig file on SERVERB slightly:
1) Altered the hostname
2) Altered the number of processors SERVERA had 4 CPUs, SERVERB only 2 CPUs
Also you have to alter the sqlhosts file to reflect the new hostname.
As SERVERB had only 256MB of mem (vs. 1024 MB on SERVERA), I used onmonitor to tune down the amount of memory needed by the server.
We still can switch easily between the to servers using separate onconfig and sqlhosts files.
Thx again, all