Performance Schema Connection Attribute Tables On the server side, these size checks on connection attribute data occur: The information in the warning message is intended to help DBAs identify clients for which attribute truncation occurred. Application programs can provide key-value connection attributes to be passed to the server at connect time. For descriptions of common attributes, see Section 27.12.9, “Performance Schema Connection Attribute Tables” . The  session_account_connect_attrs  table contains connection attributes only for the current session, and other sessions associated with the session account. To see connection attributes for all sessions, use the  session_connect_attrs  table. The  session_account_connect_attrs  table has these columns: The connection identifier for the session. The attribute name. The attribute value. The order in which the attribute was added to the set of connection attributes. 4995 • ORDINAL_POSITION • ATTR_VALUE • ATTR_NAME • PROCESSLIST_ID •A  _truncated  attribute is added to the session attributes with a value indicating how many bytes were lost, if the attribute buffer has sufficient space. This enables the Performance Schema to expose per-connection truncation information in the connection attribute tables. This information can be examined without having to check the error log. •The Performance Schema writes a message to the error log if the  log_error_verbosity  system variable is greater than 1: •The Performance Schema truncates the attribute data and increments the Performance_schema_session_connect_attrs_lost  status variable, which indicates the number of connections for which attribute truncation occurred. •For accepted connections, the Performance Schema checks aggregate attribute size against the value of the  performance_schema_session_connect_attrs_size  system variable. If attribute size exceeds this value, these actions take place: •The server imposes a limit of 64KB on the aggregate size of connection attribute data it accepts. If a client attempts to send more than 64KB of attribute data, the server rejects the connection. Otherwise, the server considers the attribute buffer valid and tracks the size of the longest such buffer in the Performance_schema_session_connect_attrs_longest_seen  status variable. Connection attributes of length  N  were truncated ( N  bytes lost) for connection  N , user  user_name @ host_name (as  user_name ), auth: {yes|no} 27.12.9.1 The session_account_connect_attrs Table