A mandatory read message is determined by a server end from one or more group session messages in a temporary group of a number of temporary groups. A respective reading status associated with the mandatory read message is obtained by the server end for each group member of a plurality of group members in the temporary group. Whether a group dissolution condition is satisfied is determined by the server end and based on the respective reading status for each group member in the temporary group. In response to determining that the group dissolution condition is satisfied, the temporary group including deleting data associated with the temporary group is dissolved by the server end.