VPN_AD_MSG_SPOOL_QUOTA_EXCEED means that you have too many messages spread across your queues inside your VPN and you have hit your VPN’s configured max spool quota. Either drain/consume some messages out of your queues, or increase your VPN’s configured max spool quota.
SYSTEM_AD_MAX_MSG_CACHE_USAGE_EXCEEDED is informational only, does not indicate message loss or anything, and applications can do nothing about it. If it occurs frequently however, then the broker administrators should contact Solace Support to troubleshoot further and see what tuning options are available.