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Commands Reference, Volume 2
Administers servers based on the
Data Replication Manager (DRM), such as glbd, the replicated
version of the global location broker (GLB).
drm_admin [ -version ]
The drm_admin tool
administers servers based on the Data Replication Manager (DRM) such as
glbd, the replicated version of the global location broker
(GLB).
With drm_admin, you can
inspect or modify replica lists, merge databases to force convergence among
replicas, stop servers, and delete replicas.
The role of drm_admin
is to administer the replication of databases, not to change the data they
contain. For instance, you can use drm_admin to merge two
replicas of the GLB database, but you must use lb_admin to add a
new entry to the database. Also, although drm_admin can stop
or delete a GLB replica, you must invoke glbd directly if you want
to start or create a replica.
Once invoked, drm_admin
enters an interactive mode, in which it accepts the commands described
below.
| -version
| Displays the version of NCS that this glbd belongs to, but
does not start the daemon.
|
Most drm_admin commands
operate on a default object (DefaultObj) at a default host
(DefaultHost). Together, DefaultObj and
DefaultHost specify a default replica. Defaults are
established by the set command and are remembered until changed by another
set.
Currently, the only known object
is GLB.
Some drm_admin commands
operate on a host other than the default. We identify this host as
OtherHost.
The host name you supply as a
DefaultHost or an OtherHost takes the form
Family:Host, where the host can be specified either by its
name or by its network address. For example,
ip:jeeves, ip:bertie, and
ip:#192.5.5.5 are acceptable host
names.
| addrep
OtherHost
| Adds OtherHost to the replica list at
DefaultHost. The replica at DefaultHost will
propagate OtherHost to all other replica lists for
DefaultObj.
|
| chrep -from
OtherHost -to NewOtherHost
| Changes the network address for OtherHost in the replica list
at DefaultHost to NewOtherHost. The replica at
DefaultHost will propagate this change to all other replica lists
for DefaultObj. The chrep command will fail if a
replica of DefaultObj is running at OtherHost or if
OtherHost is not on the replica list at
DefaultHost.
|
| delrep
OtherHost
| Deletes the replica of DefaultObj at
OtherHost. The delrep command tells the replica
at OtherHost to:
- Propagate all of the entries in its propagation
queue.
- Propagate a delete request to all other replicas,
causing OtherHost to be deleted from all other replica lists for
DefaultObj.
- Delete its copy of DefaultObj.
- Stop running.
The delrep command
returns you immediately to the drm_admin prompt, but the actual
deletion of the replica can take a long time in configurations that are not
stable and intact. You can check whether the daemon for the deleted
replica has stopped by listing the processes running on its host.
|
| info
| Gets status information about the replica for DefaultObj at
DefaultHost.
|
| lrep [-d]
[-clocks] [-na]
| Lists replicas for DefaultObj as stored in the replica list at
DefaultHost.
- -d
- Lists deleted as well as existing replicas.
- -clocks
- Shows the current time on each host and indicates clock skew among the
replicas.
- -na
- Lists the network address of each host.
|
| merge
{-from | -to} OtherHost
| Copies entries in the DefaultObj database and replica list
from one replica to another. It copies an entry if no corresponding
entry exists in the destination database or if the corresponding entry in the
destination database bears an earlier timestamp.
A merge does not cause entries to
be propagated. The database and replica list at the origination are not
changed.
The -from option copies
entries from the DefaultObj database and replica list at
OtherHost to the DefaultObj database and replica list at
DefaultHost.
The -to option copies
entries from the database and replica list at DefaultHost to the
database and replica list at OtherHost.
A merge -from followed
by a merge -to causes the replicas at the two hosts to
converge.
|
| merge_all
| Uses DefaultHost as the hub for a global merge of all replicas
for DefaultObj. For each host on the replica list at
DefaultHost, a merge_all first does a merge
-from, then does a merge -to. All replicas of
DefaultObj are thereby forced into a consistent state. The
merge_all operation does not cause any entries to be
propagated.
You should do a
merge_all when:
A replica is purged.
A replica is reset.
A replica has been inaccessible
for two weeks or more.
A replica has become physically
inaccessible (for example, when its database is destroyed by a disk failure)
|
| monitor [-r
n]
| This command causes drm_admin to read the clock of each
replica of DefaultObj every n minutes and to report any clock skews
or nonanswering replicas. If you do not specify -r, the
period is 15 minutes.
|
| purgerep
OtherHost
| Purges OtherHost from the replica list at
DefaultHost. The replica at DefaultHost then
propagates a delete request to the replicas at the hosts remaining on its
list, thereby removing OtherHost from all other replica lists for
DefaultObj. The delete request is not sent to
OtherHost.
A purgerep can cause
data to be lost and should only be used when a replica has become physically
inaccessible. You should do a merge_all operation after
the purgerep to prevent the remaining replicas of the
DefaultObj database from becoming inconsistent. If the
purged replica is still running, it should be reset.
We recommend that you use
chrep (rather than addrep and purgerep) to
change entries on the replica list.
|
| quit
| Quits the drm_admin session.
|
| reset
OtherHost
| Resets the replica of DefaultObj at
OtherHost.
The reset command tells
the replica at OtherHost to delete its copy of
DefaultObj and to stop running. It does not cause
OtherHost to be deleted from any other replica lists. This
command can cause data to be lost unless a successful merge_all is
done first.
|
| set
[-o ObjName] -h HostName
| Sets the default object and host. All subsequent commands will
operate on ObjName. Subsequent commands that do not specify
a host will be sent to HostName. If you do not specify the
-o option, drm_admin keeps the current
DefaultObj.
If you use set with the
-o option, drm_admin checks the clocks at all hosts with
replicas of the specified object.
|
| stop
| Stops the server for DefaultObj that is running at
DefaultHost.
|
The following example starts
drm_admin, sets the default object to GLB, and sets the default
host to mars:
/etc/ncs/drm_admin drm_admin: set -o glb -h dds:mars
Default object: glb default host: dds:mars
state: in service
Checking clocks of glb replicas
dds:mars 1987/04/09.17:09
dds:pluto 1987/04/09.17:09
dds:mercury 1987/04/09.17:07
The lb_admin command.
The glbd (NCS) daemon
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