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VVR provides the following modes of SRL overflow protection: autodcm, dcm, or override. VVR activates these modes only when the SRL overflows. You can set up SRL protection by setting the srlprot attribute of the corresponding RLINKs to autodcm, dcm, or override. By default, the srlprot attribute is set to autodcm. The following table summarizes how the state of the RLINK affects SRL protection when the SRL is about to overflow:
* Protect by stalling application writes until SRL drains 5% to 95% full or drains 20 megabytes, whichever is smaller.
If the SRL overflow protection is set to autodcm, override, or dcm, SRL overflow protection is enabled. The replication setting for the Secondary and the state of the connection between the Primary and the Secondary determines how VVR works when the SRL is about to overflow.
VVR activates the DCM irrespective of whether the Primary and Secondary are connected or disconnected. Each data volume in the RVG must have a DCM; note that VVR does not stall writes when srlprot is set to autodcm.
If the Primary and Secondary are connected, new writes are stalled in the operating system of the Primary host until a predetermined amount of space, that is 5% or 20 MB, whichever is less, becomes available in the SRL.
If the Primary and Secondary are disconnected, DCM protection is activated and writes are written to the DCM. Each data volume in the RVG must have a DCM.
If the Primary and Secondary are connected, new writes are stalled in the operating system of the Primary host until a predetermined amount of space, that is 5% or 20 MB, whichever is less, becomes available in the SRL.
If the Primary and Secondary are disconnected, VVR disables SRL protection and lets the SRL overflow.
For more information, see Setting the SRL overflow protection.