Example 6-1 shows how to change gmlinktolerance and the  gmmaxhostdelay parameters using the chsystem  command. 

chsystem -gmlinktolerance 30 chsystem -gmmaxhostdelay 100 

Test and monitor:  To reiterate, thoroughly test and carefully monitor the host impact of any changes like these before putting them into a live production environment. 

A detailed description and settings considerations about the gmlinktolerance and the gmmaxhostdelay parameters are described in 6.3.5, “1920 error” on page 203. 

## rcbuffersize 

rcbuffersize  was introduced with the version 6.2 code level so that systems with intense and bursty write I/O would not fill the internal buffer while Global Mirror writes were undergoing sequence tagging. 

Important:  Do not change the rcbuffersize parameter except under the direction of IBM Support. 

Example 6-2 shows how to change rcbuffersize  to 64 MB by using the chsystem  command. The default value for rcbuffersize  is 48 MB and the maximum is 512 MB. 

chsystem -rcbuffersize 64 

Remember that any additional buffers you allocate are taken away from the general cache. 

## maxreplicationdelay and partnershipexclusionthreshold 

IBM Spectrum Virtualize uses two parameters, maxreplicationdelay  and partnershipexclusionthreshold , for remote copy advanced tuning. 

maxreplicationdelay  is a system-wide parameter that defines a maximum latency (in seconds) for any individual write passing through the Global Mirror logic. If a write is hung for that time, for example due to a rebuilding array on the secondary system, Global Mirror stops the relationship (and any containing consistency group), triggering a 1920 error. 

The partnershipexclusionthreshold  parameter was introduced to allow users to set the timeout for an I/O that triggers a temporarily dropping of the link to the remote cluster. The value must be a number from 30 - 315. 

Important:  Do not change the partnershipexclusionthreshold parameter except under the direction of IBM Support. 

A detailed description and settings considerations about the maxreplicationdelay parameter are described in 6.3.5, “1920 error” on page 203. 

