02-08-2018 07:37 PM
I need help on my replication issue. We just move the server on the other site after the replication had finished. I paused the replication before moving the hardware. After I resumed and resynchronized the RLINK, data volumes used DCM instead of SRL. Please see below commands and attached images.
I'm using InfoScale Enterprise 7.0.1 running on Windows 2008 Server R2.
1. Primary (SVR1)
vxrlink -g <diskgroup> status <RLINK>
RLINK has a full Replicator Log. 13% (1234567891) DCM is used.
2. Secondary (SVR2)
02-08-2018 08:35 PM
Just called the Veritas support. We just changed the protocol from UDP/IP to TCP/IP on the VEA consoole.
DCM is now draining.
02-12-2018 08:34 PM
The way to reply DCM log is to run the command below
vradmin -g <dg_name> resync >rvg_name>
resync Starts replay an active DCM in the Replicated Data Set (RDS) rvg.
The resync command starts replay of a DCM that is active due to SRL overflow or failback logging. Replay occurs for all RLINKs on which the dcm_logging flag is set. If any of these RLINKs are disconnected or paused, resynchronization is delayed until this condition clears. Detaching a disconnected or paused RLINK clears the dcm_logging flag, and allows resynchronization to proceed on any remaining RLINKs.
The resync keyword can optionally be used with the cache or cachesize attributes to to create a space-optimized snapshot of the secondary data volumes before starting the resynchronization process.
VVR exchanges two types of messages between the Primary and the Secondary: heartbeat messages and data messages. The heartbeat messages are transmitted using the UDP transport protocol. VVR can use either the TCP transport protocol or the UDP transport protocol to exchange data messages.
The choice of protocol to use for the data messages is based on the network characteristics. TCP has been found to perform better than UDP on networks that lose packets. However, you must experiment with both protocols to determine the one that performs better in your network environment.
When using the TCP protocol, VVR creates multiple connections, if required, to use the available bandwidth. This is especially useful if there are many out of order packets.
You must specify the same protocol for the Primary and Secondary; otherwise, the nodes cannot communicate and the RLINKs do not connect. This also applies to all nodes in a cluster environment.
VVR uses the UDP transport protocol by default. For information on how to set the network protocol,
General peaking, if your VVR goes to DCM mode on a regular basis, you need to review your network bandwidth, application data bandwidth and the size of SRL. If the application keeps generating new data in a rate much higher than the data replication bandwidth and the SRL is now big enough, you will see frequently replication witched to DCM logging or overflow.