i think that this settings in on a role base level.
you can create a role just for this user and add it to him / her
this settings controls it on a role level basis: authorize.conf
srchDiskQuota = <number> * Maximum amount of disk space (MB) that can be used by search jobs of a user that belongs to this role * In search head clustering environments, this setting takes effect on a per-member basis. There is no cluster-wide accounting. * The dispatch manager checks the quota at the dispatch time of a search and additionally the search process will check at intervals that are defined in the 'disk_usage_update_period' setting in limits.conf as long as the search is active. * The quota can be exceeded at times, since the search process does not check the quota constantly. * Exceeding this quota causes the search to be auto-finalized immediately, even if there are results that have not yet been returned. * Defaults to '100', for 100 MB.