Quick Help: TNS - 12519 TNS: no appropriate service handler found
If you get a “TNS - 12519 TNS: no appropriate service handler found” the very first thing to check is the max session/processes.
select * from v$resource_limit RESOURCE_NAME CURRENT_UTILIZATION MAX_UTILIZATION INITIAL_AL LIMIT_VALU ------------------------------ ------------------- --------------- ---------- ---------- processes 47 300 300 300 sessions 52 309 335 335 enqueue_locks 34 91 5008 5008 enqueue_resources 53 260 2514 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 59 454 1472 UNLIMITED temporary_table_locks 0 23 UNLIMITED UNLIMITED transactions 1409 1442 368 UNLIMITED branches 0 16 368 UNLIMITED cmtcallbk 0 3 368 UNLIMITED sort_segment_locks 0 40 UNLIMITED UNLIMITED max_rollback_segments 29 58 368 65535 max_shared_servers 1 1 UNLIMITED UNLIMITED parallel_max_servers 0 8 8 3600
As it is visible at MAX_UTILIZATION for processes the maximum processes was once reached.
Just increase it an restart your database.
alter system set processes=600