In SRM, array managers beget arrays. Arrays then beget array pairs. Array pairs then beget replicated devices. In order for replication devices to be discovered, you need to enable the array pairs that participate in that replication.
Enabling an Array Pair
In order for an array pair to be enabled, one array must be locally discovered by an array manager on one SRM server in an SRM pair, and the other array in that replication pair must be discovered by a separate array manager on the opposing SRM server. If both arrays are discovered as local to the same SRM server, it cannot be enabled. If one of the two arrays are not discovered at all, then the pair cannot be enabled. Finally, there also must be replication between both arrays. If replication is not enabled between FlashArray A and FlashArray B (even if the array managers are properly configured), the replication pair cannot be enabled, because, well, there is no replication.
Take the instance below:
When selected, it cannot be enabled:
The pair flasharray-m50-1 to flasharray-m20-2 is an identified replication pair, but cannot be enabled. Why? Well if you look at the Array Manager Pair column, only one SRM server (or more accurately only one array manager) can find that pair. The other SRM server does not have an array manager that sees that pair too. Therefore, you need to either create an array manager on that SRM server that has access to flasharray-m20-2, or make sure an existing array manager can access it.
Note that the array in an array pair that does not have a corresponding array manager will also display the array serial number next to the name in the listing.
If a given array pair is seen on both sites (indicated that the array manager column lists two array managers) it can be enabled.
Select the pair, click on Array Pair, and click Enable.
Once enabled, the pair will show as enabled and the SRA will discover all devices in that replication pair.
The next question is likely: "Should I enable all discovered array pairs?". In general, the recommendation is to enable just the array pairs that you need. Each pair that you enable will cause discoveries to occur. If you do not plan on using any devices in that pair, there is no reason to enable it--it just causes unnecessary work in SRM discovery time.
Disabling an Array Pair
If an array pair is no longer needed (permanently or temporarily) you can disable the array pair. This will ensure no recovery plans are built on top of that pair. In order though for an array pair to be disabled it must not be in use. An array pair is considered to be "in-use" if there are any replication devices discovered from that pair in a SRM protection group.
A disable operation will fail return the below error if it is in-use:
You can verify a pair is not in-use by selecting it and then verifying that no protection groups are listed in the Protection Group column of the Discovered Devices table:
If that is clear, it is safe to select the array pair, click the Array Pair drop down and choose Disable.