> # Compacting the Zone Database for Downgrading

> Prior to Cisco SAN-OS Release 3.0(1), only 2000 zones are supported per VSAN. If you add more than 2000 zones to a VSAN, a configuration check is registered to indicate that downgrading to a previous release could cause you to lose the zones over the limit. To avoid the configuration check, delete the excess zones and compact the zone database for the VSAN. If there are 2000 zones or fewer after deleting the excess zones, the compacting process assigns new internal zone IDs and the configuration can be supported by Cisco SAN-OS Release 2.x or earlier. Perform this procedure for every VSAN on the switch with more than 2000 zones.

> Note A merge failure occurs when a switch supports more than 2000 zones per VSAN but its neighbor does not. Also, zone set activation can fail if the switch has more than 2000 zones per VSAN and not all switches in the fabric support more than 2000 zones per VSAN.

> To compact the zone database for downgrading, refer to the Cisco MDS 9000 Family NX-OS Fabric Configuration Guide.

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