Error Message

1. replication gets into dcm logging mode

2. vxconfigd seems to hang

Jul  6 03:10:05 mrknbemauxpr05 vxio: [ID 603206 kern.warning] WARNING: VxVM vxio V-5-3-0 commit: Timedout abort the transaction!
Jul  6 03:10:05 mrknbemauxpr05 vxio: [ID 915177 kern.warning] WARNING: VxVM vxio V-5-3-0 commit: Timedout waiting for rvg netbackup_rvg
to quiesce, count 1

3. VCS agents timeout

latencyprotection for VVR is set to off

bash-2.05$ pwd
/evidence/mtv/09/412-443-209/VRTSexplorer_84d4d4ec_mrknbemauxpr05/vxvm
bash-2.05$ grep latencyprot vxprint_Pl
          synchronous=off latencyprot=off srlprot=autodcm
          synchronous=off latencyprot=off srlprot=autodcm
bash-2.05$

The UDP packets or TCP packets transmitted by VVR that are of size greater than the network Maximum Transmission Unit (MTU) are broken up into IP packets of MTU size by the IP module of the operating system. There may be losses on the network because the packets are going through routers that do not support IP fragmentation and have a smaller MTU than your network device. In this case, make the MTU size the same as the MTUsize of the router with the smallest MTU in the network.

Choosing the packet size

If you have selected the UDP transport protocol for replication, the UDP packet size used by VVR to communicate between hosts could be an important factor in the replication performance. By default, VVR uses a UDP packet size of 8400 bytes.

In certain network environments, such as those that do not support fragmented IP packets, it may be necessary to decrease the packet size. If the network you are using loses many packets, the effective bandwidth available for replication is reduced. You can tell that this is happening if you run vxrlink stats on the RLINK, and see many timeout errors.
In this case, network performance may be improved by reducing the packet size. If the network is losing many packets, it may simply be that each time a large packet is lost, a large retransmission has to take place. In this case, try reducing the packet size until the problem is ameliorated.

If some element in the network, such as IPSEC or VPN hardware, is adding to the packets, reduce the packet size so that there is space for the additional bytes in the packet, and the MTU is not exceeded. Otherwise, each packet is broken into two.

To set the packet_size:
 

# vradmin -g diskgroup set local_rvgname sec_hostname packet_size=n

The argument local_rvgname is the name of the RVG on the local host and represents the RDS.
The argument sec_hostname is the name of the Secondary host as displayed in the output of the vradmin printrvg command.
The argument n represents the packet size in bytes.
The minimum value for the packet_size is 1300 bytes.
The maximum value of the packet_size is 65464 bytes.