Rlink in DCM mode

Veritas VVR replication note for RLINK / DCM mode alerts.

Use this page when an alert says that an RLINK is in DCM mode.

Example alert pattern:

[CRITICAL]: Rlink RLINK_NAME in DISK_GROUP/RVG_NAME in DCM mode

Sanitized example:

[CRITICAL]: Rlink to_sitel in vomdg/vomdb_rvg in DCM mode

What this means

An RLINK in DCM mode means Veritas Volume Replicator is using DCM tracking for replication changes.

This needs investigation because replication may not be in the normal healthy state.

Do not assume data is fully healthy until replication status is checked.

First check replication status

Command pattern:

vradmin -g DISK_GROUP repstatus RVG_NAME

Example:

vradmin -g vomdg repstatus vomdb_rvg

Healthy output to look for

Good signs:

Data status:                consistent, up-to-date
Replication status:         replicating (connected)
Timestamp Information:      behind by  0h 0m 0s

If you see this, replication is likely OK.

Example sanitized output

Replicated Data Set: vomdb_rvg

Primary:
  Host name:                  PRIMARY_HOST_OR_IP
  RVG name:                   vomdb_rvg
  DG name:                    vomdg
  RVG state:                  enabled for I/O
  Data volumes:               3
  VSets:                      0
  SRL name:                   SRL
  SRL size:                   200.00 G
  Total secondaries:          1

Secondary:
  Host name:                  SECONDARY_HOST_OR_IP
  RVG name:                   vomdb_rvg
  DG name:                    vomdg
  Data status:                consistent, up-to-date
  Replication status:         replicating (connected)
  Current mode:               asynchronous
  Logging to:                 SRL
  Timestamp Information:      behind by  0h 0m 0s

If vradmin cannot connect

Check cluster status:

hastatus -sum

Then check:

hagrp -state
hares -state
service vras-vradmind status

Things to check:

Is the service group online?
Is a related resource offline or faulted?
Is the correct node active?
Is vras-vradmind running?

If vras-vradmind is failed

Check:

service vras-vradmind status

Problem example:

VxVM VVR  V-5-4-0 VRAS daemon running: [  FAILED  ]
VxVM VVR  V-5-4-0 vvr_stats running: [  OK  ]

Restart:

service vras-vradmind restart

Verify:

service vras-vradmind status
vradmin -g DISK_GROUP repstatus RVG_NAME

If replication is not healthy

If output does not show:

Data status:                consistent, up-to-date
Replication status:         replicating (connected)

then investigate or escalate.

Do not clear faults, switch groups, or restart cluster services blindly.

Useful log checks

sudo tail -n 100 /var/log/messages
sudo grep -i "rlink" /var/log/messages
sudo grep -i "dcm" /var/log/messages
sudo grep -i "vras" /var/log/messages
sudo grep -i "vradmind" /var/log/messages
journalctl -xe

Safe troubleshooting flow

1. Read the alert.
2. Identify RLINK_NAME, DISK_GROUP, and RVG_NAME.
3. Run vradmin repstatus.
4. Check Data status.
5. Check Replication status.
6. Check Timestamp Information.
7. If vradmin cannot connect, check hastatus -sum.
8. Check hagrp and hares state.
9. Check vras-vradmind status.
10. Restart vras-vradmind only if it is failed and this matches the known fix.
11. Run vradmin repstatus again.
12. If still not OK, escalate or follow internal procedure.

Commands to remember

vradmin -g DISK_GROUP repstatus RVG_NAME
hastatus -sum
hagrp -state
hares -state
service vras-vradmind status
service vras-vradmind restart