ORA-00020錯誤是由於程式數設定過低，導致程式數用完，資料庫無法連線不上，從而爆出ora-00020錯誤。

11g 11.2.0.4版本

使用者系統需要的程式數，上線前一次性設定完畢！

SYS@orcl>show parameter process;

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

aq_tm_processes integer 1

cell_offload_processing boolean TRUE

db_writer_processes integer 1

gcs_server_processes integer 0

global_txn_processes integer 1

job_queue_processes integer 1000

log_archive_max_processes integer 8

processes integer 40

processor_group_name string

SYS@orcl>select count(*) from v$process;

COUNT(*)

----------

34

最大可用程式數40-34=6個其實可用只有5個

11.2.0.4中發現processes最少不能少於40個 process程式數至少有32個以上設定processes少於40個將預設設定為40

實驗中我設定processes=10，最後顯示結果

SYS@orcl>alter system set processes=10 scope=spfile;

System altered.

SYS@orcl>shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SYS@orcl>startup ;

ORACLE instance started.

Total System Global Area 1503199232 bytes

Fixed Size 2253424 bytes

Variable Size 905973136 bytes

Database Buffers 587202560 bytes

Redo Buffers 7770112 bytes

Database mounted.

Database opened.

SYS@orcl>show parameter processes;