About the srlprot attribute


About the srlprot attribute
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VVR provides the following modes of SRL overflow protection: autodcm, dcm, fail, 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, fail, or override. By default, the srlprot attribute is set to autodcm.To disable SRL protection, set the srlprot attribute to off.

Table: SRL protection and the state of the RLINK summarizes how the state of the RLINK affects SRL protection when the SRL is about to overflow.

Table: SRL protection and the state of the RLINK

Value of the srlprot Attribute	When RLINK is Connected	When RLINK is Disconnected
autodcm	Convert to DCM logging	Convert to DCM logging
dcm	Protect Protects by stalling application writes until SRL drains 5% to 95% full or drains 20 megabytes, whichever is smaller.	Convert to DCM logging
fail	SRL protection is enabled.	Write requests are failed with an EIO error
off	SRL protection is disabled.	SRL protection is disabled.
override	Protect Protects by stalling application writes until SRL drains 5% to 95% full or drains 20 megabytes, whichever is smaller.	Overflow

If the SRL overflow protection is set to autodcm, dcm, fail, or override, 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.

srlprot=autodcm

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.

srlprot=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, DCM protection is activated and writes are written to the DCM. Each data volume in the RVG must have a DCM.

srlprot=fail

If the Primary and Secondary are connected, SRL protection is enabled. If the RLINK becomes inactive for any reason, and SRL overflow is imminent, subsequent write requests are failed with an EIO error.

srlprot=override

srlprot=off

SRL overflow protection is disabled, regardless of whether the Primary and Secondary are connected or disconnected.

If the Primary and Secondary are disconnected, VVR disables SRL protection and lets the SRL overflow.