• The following error is displayed when editing Application Firewall Profile:

           "communication error with aslearn"

• New rules are not being learned. 
• The following is recorded in /var/nslog/aslearn.log file on NetScaler:

@(#)Netscaler Learning Server (aslearn) NS11.0: Build 62.10, Date: Aug  8 2015, 22:11:53 (release) [FreeBSD]
errno = 275
Per violation db count exceeded for profile www.appfw.com.yz and starturl check; Skipping the db request.
Per violation db count exceeded for profile www.appfw.com.yz and ff check; Skipping the db request.
aslearn: Learning request failed

• The following is the log from ns.log file:

CMD_EXECUTED 4047 0 :  User nsroot - Remote_ip x.x.x.x- Command "show appfw learningdata www.appfw.com.yz startURL" - Status "ERROR: Communication error with aslearn"

1.  Create a new Application Firewall profile (new name) and bind it to the Application Firewall policy.
   This will clear existing learned database.

2. To remove existing learned database, go to Application Firewall > Application firewall Engine Settings.> Reset learned data.
   or 
   Run the below command :
   
   "reset appfw learningdata"

Problem Cause

The database learning limit is reached as mentioned in below link:

"The learning database is limited to 20 MB in size, which is reached after approximately 2,000 learned rules or relaxations are generated per security check for which learning is enabled​"

https://docs.citrix.com/en-us/netscaler/11-1/application-firewall/profiles/learning.html