I'm running into this error on my Sitecore prod CD instance, as well as its failover:
ERR Error running script (call to f_f61bd104cdd24acf438fe02407a37f4334659383): @user_script:4: @user_script: 4: -OOM command not allowed when used memory > 'maxmemory'.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
Exception Details: StackExchange.Redis.RedisServerException: ERR Error running script (call to f_f61bd104cdd24acf438fe02407a37f4334659383): @user_script:4: @user_script: 4: -OOM command not allowed when used memory > 'maxmemory'.
I saw this article pop up, which was mostly about monitoring: Sitecore fails when memory > maxmemory in Redis. At the moment our prod instances are in development and we're building them out, so there's no traffic to speak of. When we spun up the failover instance, originally both were pointing to the same Redis cache, but I created a failover one and changed the connection string to separate them. Now after a deployment, the message returned.
We were using the basic 1GB tier, which we're updating to C2 now, but beyond that, is there any way to better manage this? Also, what is the Redis cache really used for, and is there a benefit to it or could we turn it off if it's being an impediment?