To find the number max number of sessions reached run the command below, note that this view will hold the information up to the last restart of the database:
SQL> select * from v$resource_limit;
RESOURCE_NAME CURRENT_UTILIZATION MAX_UTILIZATION INITIAL_AL LIMIT_VALU
------------------------------ ------------------- --------------- ---------- ----------
processes 37 47 150 150
sessions 45 58 248 248
enqueue_locks 28 297 3080 3080
enqueue_resources 19 50 1308 UNLIMITED
ges_procs 0 0 0 0
ges_ress 0 0 0 UNLIMITED
ges_locks 0 0 0 UNLIMITED
ges_cache_ress 0 0 0 UNLIMITED
ges_reg_msgs 0 0 0 UNLIMITED
ges_big_msgs 0 0 0 UNLIMITED
ges_rsv_msgs 0 0 0 0
gcs_resources 0 0 0 0
gcs_shadows 0 0 0 0
dml_locks 0 0 1088 UNLIMITED
temporary_table_locks 0 3 UNLIMITED UNLIMITED
transactions 2 2 272 UNLIMITED
branches 0 0 272 UNLIMITED
cmtcallbk 2 3 272 UNLIMITED
max_rollback_segments 11 11 272 65535
sort_segment_locks 0 8 UNLIMITED UNLIMITED
k2q_locks 0 0 496 UNLIMITED
max_shared_servers 1 1 UNLIMITED UNLIMITED
parallel_max_servers 0 0 40 3600
SQL> select * from v$resource_limit;
RESOURCE_NAME CURRENT_UTILIZATION MAX_UTILIZATION INITIAL_AL LIMIT_VALU
------------------------------ ------------------- --------------- ---------- ----------
processes 37 47 150 150
sessions 45 58 248 248
enqueue_locks 28 297 3080 3080
enqueue_resources 19 50 1308 UNLIMITED
ges_procs 0 0 0 0
ges_ress 0 0 0 UNLIMITED
ges_locks 0 0 0 UNLIMITED
ges_cache_ress 0 0 0 UNLIMITED
ges_reg_msgs 0 0 0 UNLIMITED
ges_big_msgs 0 0 0 UNLIMITED
ges_rsv_msgs 0 0 0 0
gcs_resources 0 0 0 0
gcs_shadows 0 0 0 0
dml_locks 0 0 1088 UNLIMITED
temporary_table_locks 0 3 UNLIMITED UNLIMITED
transactions 2 2 272 UNLIMITED
branches 0 0 272 UNLIMITED
cmtcallbk 2 3 272 UNLIMITED
max_rollback_segments 11 11 272 65535
sort_segment_locks 0 8 UNLIMITED UNLIMITED
k2q_locks 0 0 496 UNLIMITED
max_shared_servers 1 1 UNLIMITED UNLIMITED
parallel_max_servers 0 0 40 3600