比较少遇到打开一个数据库报ORA-00020: maximum number of processes () exceeded,导致open数据库失败

SQL> alter database open;
alter database open
*
第 1 行出现错误:
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-00450: background process 'QMNC' did not start
ORA-00444: background process "QMNC" failed while starting
ORA-00020: maximum number of processes () exceeded
进程 ID: 6340
会话 ID: 109 序列号: 3

看这个报错应该是由于进程数达到了限制，导致在open数据库过程中启动后台进程QMNC失败,导致open过程失败,分析进程数不足的原因,查看启动时候的参数配置

Fri Dec 26 16:48:27 2025
Adjusting the default value of parameter parallel_max_servers
from 2560 to 135 due to the value of parameter processes (150)
Starting ORACLE instance (normal)
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Picked latch-free SCN scheme 3
Fri Dec 26 16:48:38 2025
Using LOG_ARCHIVE_DEST_1 parameter default value as USE_DB_RECOVERY_FILE_DEST
Autotune of undo retention is turned on. 
IMODE=BR
ILAT =28
LICENSE_MAX_USERS = 0
SYS auditing is disabled
Starting up:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options.
Windows NT Version V6.2  
CPU                 : 64 - type 8664, 32 Physical Cores
Process Affinity    : 0x0x0000000000000000
Memory (Avail/Total): Ph:82501M/130752M, Ph+PgF:103658M/150208M 
Using parameter settings in client-side pfile D:\PFILE.TXT on machine HISSERVER
System parameters with non-default values:
  processes                = 150
  sga_target               = 39296M
  control_files            = "D:\ORACLE64\ORADATA\ORA817\CONTROL01.CTL"
  control_files            = "D:\ORACLE64\RECOVERY_AREA\ORA817\CONTROL02.CTL"
  db_block_size            = 8192
  compatible               = "11.2.0.0.0"
  db_recovery_file_dest    = "D:\ORACLE64\recovery_area"
  db_recovery_file_dest_size= 4122M
  undo_tablespace          = "UNDOTBS1"
  remote_login_passwordfile= "EXCLUSIVE"
  db_domain                = ""
  dispatchers              = "(PROTOCOL=TCP) (SERVICE=ora817XDB)"
  audit_file_dest          = "D:\ORACLE64\ADMIN\ORA817\ADUMP"
  audit_trail              = "DB"
  db_name                  = "ora817"
  open_cursors             = 300
  pga_aggregate_target     = 13075M
  diagnostic_dest          = "D:\ORACLE64"
Fri Dec 26 16:49:10 2025
PMON started with pid=2, OS id=1992 
Fri Dec 26 16:49:10 2025
PSP0 started with pid=3, OS id=6744 
Fri Dec 26 16:49:12 2025
VKTM started with pid=4, OS id=7592 at elevated priority
Fri Dec 26 16:49:12 2025
GEN0 started with pid=5, OS id=7780 
Fri Dec 26 16:49:12 2025
DBRM started with pid=7, OS id=5372 
Fri Dec 26 16:49:12 2025
MMAN started with pid=9, OS id=6700 
Fri Dec 26 16:49:12 2025
DBW0 started with pid=10, OS id=1920 
Fri Dec 26 16:49:12 2025
DBW1 started with pid=11, OS id=4476 
Fri Dec 26 16:49:12 2025
DBW2 started with pid=12, OS id=6788 
Fri Dec 26 16:49:12 2025
DBW3 started with pid=13, OS id=4608 
Fri Dec 26 16:49:12 2025
DBW4 started with pid=14, OS id=6716 
Fri Dec 26 16:49:12 2025
DBW5 started with pid=15, OS id=6252 
Fri Dec 26 16:49:12 2025
DBW6 started with pid=16, OS id=7948 
Fri Dec 26 16:49:12 2025
DBW7 started with pid=17, OS id=5868 
Fri Dec 26 16:49:12 2025
LGWR started with pid=18, OS id=1644 
Fri Dec 26 16:49:12 2025
CKPT started with pid=19, OS id=5704 
Fri Dec 26 16:49:12 2025
SMON started with pid=20, OS id=4532 
Fri Dec 26 16:49:12 2025
RECO started with pid=21, OS id=380 
Fri Dec 26 16:49:12 2025
MMON started with pid=22, OS id=1316 
Fri Dec 26 16:49:12 2025
MMNL started with pid=23, OS id=6108 
Fri Dec 26 16:49:12 2025
DIAG started with pid=6, OS id=7904 
Fri Dec 26 16:49:12 2025
starting up 1 dispatcher(s) for network address '(ADDRESS=(PARTIAL=YES)(PROTOCOL=TCP))'...
starting up 1 shared server(s) ...
ORACLE_BASE from environment = D:\ORACLE64

这里可以看出来数据库版本是11.2.0.3,processes配置为默认值150.进一步查看启动报错时候的alert日志

ALTER DATABASE RECOVER  database  
Media Recovery Start
 started logmerger process
Fri Dec 26 17:03:44 2025
Media Recovery failed with error 264
Slave exiting with ORA-283 exception
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_pr00_344.trc:
ORA-00283: recovery session canceled due to errors
ORA-00264: no recovery required
Recovery Slave PR00 previously exited with exception 283
ORA-283 signalled during: ALTER DATABASE RECOVER  database  ...
alter database open
Fri Dec 26 17:03:48 2025
Thread 1 opened at log sequence 37301
  Current log# 2 seq# 37301 mem# 0: D:\ORACLE64\ORADATA\ORA817\REDO02.LOG
Successful open of redo thread 1
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
Fri Dec 26 17:03:49 2025
SMON: enabling cache recovery
[6340] Successfully onlined Undo Tablespace 2.
Undo initialization finished serial:0 start:5143437 end:5143718 diff:281 (2 seconds)
Verifying file header compatibility for 11g tablespace encryption..
Verifying 11g file header compatibility for tablespace encryption completed
SMON: enabling tx recovery
Fri Dec 26 17:03:49 2025
Database Characterset is ZHS16GBK
No Resource Manager plan active
replication_dependency_tracking turned off (no async multimaster replication found)
ORA-00020: maximum number of processes (150) exceeded
 ORA-20 errors will not be written to the alert log for
 the next minute. Please look at trace files to see all
 the ORA-20 errors.
Process P123 submission failed with error = 20
Starting background process QMNC
Process QMNC submission failed with error = 20
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_ora_6340.trc:
ORA-00444: 后台进程 "QMNC" 启动失败
ORA-00020: 超出最大进程数 ()
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_ora_6340.trc:
ORA-00450: 后台进程 'QMNC' 未启动
ORA-00444: 后台进程 "QMNC" 启动失败
ORA-00020: 超出最大进程数 ()
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_ora_6340.trc:
ORA-00450: 后台进程 'QMNC' 未启动
ORA-00444: 后台进程 "QMNC" 启动失败
ORA-00020: 超出最大进程数 ()
Error 450 happened during db open, shutting down database
USER (ospid: 6340): terminating the instance due to error 450
Fri Dec 26 17:03:50 2025
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_p036_8044.trc  (incident=4105):
ORA-01578: ORACLE data block corrupted (file # 9, block # 504643)
ORA-01110: data file 9: 'D:\ORACLE64\ORADATA\ORA817\HRPRUN_DATA05.DBF'
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_4105\ora817_p036_8044_i4105.trc
Fri Dec 26 17:03:50 2025
Process m000 submission failed with error = 20
Fri Dec 26 17:04:07 2025
Instance terminated by USER, pid = 6340
ORA-1092 signalled during: alter database open...
opiodr aborting process unknown ospid (6340) as a result of ORA-1092
Fri Dec 26 17:04:09 2025
ORA-1092 : opitsk aborting process

看alert日志比较明显有Process P123 submission failed with error = 20提示,这里表示启动P123进程时候也遭遇到了进程数不足的限制导致该进程无法启动,而Pxxx进程是oracle的并行进程(而且在后面还报了由于坏块导致P036进程报错的信息),也就是说这个数据库在启动过程中启动了大量的并行进程(至少122个已经启动),这也就是说明了为什么150个进程不足的原因.在数据库完成实例恢复,完全open之前启动并行进程进行恢复的,很可能就是并行回滚操作.为了进一步验证猜想,把processes调整到1500,然后尝试启动库

Fri Dec 26 17:06:44 2025
alter database open
Beginning crash recovery of 1 threads
 parallel recovery started with 32 processes
Started redo scan
Completed redo scan
 read 20 KB redo, 5 data blocks need recovery
Started redo application at
 Thread 1: logseq 37301, block 18209
Recovery of Online Redo Log: Thread 1 Group 2 Seq 37301 Reading mem 0
  Mem# 0: D:\ORACLE64\ORADATA\ORA817\REDO02.LOG
Completed redo application of 0.02MB
Completed crash recovery at
 Thread 1: logseq 37301, block 18249, scn 327081807
 5 data blocks read, 5 data blocks written, 20 redo k-bytes read
Fri Dec 26 17:06:46 2025
Thread 1 advanced to log sequence 37302 (thread open)
Thread 1 opened at log sequence 37302
  Current log# 3 seq# 37302 mem# 0: D:\ORACLE64\ORADATA\ORA817\REDO03.LOG
Successful open of redo thread 1
MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
Fri Dec 26 17:06:47 2025
SMON: enabling cache recovery
[7104] Successfully onlined Undo Tablespace 2.
Undo initialization finished serial:0 start:5321812 end:5322031 diff:219 (2 seconds)
Verifying file header compatibility for 11g tablespace encryption..
Verifying 11g file header compatibility for tablespace encryption completed
SMON: enabling tx recovery
Database Characterset is ZHS16GBK
No Resource Manager plan active
replication_dependency_tracking turned off (no async multimaster replication found)
Fri Dec 26 17:06:49 2025
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_p091_5924.trc  (incident=5745):
ORA-01578: ORACLE data block corrupted (file # 9, block # 504643)
ORA-01110: data file 9: 'D:\ORACLE64\ORADATA\ORA817\HRPRUN_DATA05.DBF'
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_5745\ora817_p091_5924_i5745.trc
Starting background process QMNC
Fri Dec 26 17:06:49 2025
QMNC started with pid=156, OS id=8012 
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_p091_5924.trc  (incident=5746):
ORA-01578: ORACLE data block corrupted (file # , block # )
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_5746\ora817_p091_5924_i5746.trc
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_smon_7424.trc  (incident=4961):
ORA-01578: ORACLE data block corrupted (file # 9, block # 504643)
ORA-01110: data file 9: 'D:\ORACLE64\ORADATA\ORA817\HRPRUN_DATA05.DBF'
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_4961\ora817_smon_7424_i4961.trc
Completed: alter database open
SMON: Restarting fast_start parallel rollback
Fri Dec 26 17:06:51 2025
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_p000_5472.trc  (incident=5009):
ORA-01578: ORACLE data block corrupted (file # 9, block # 504643)
ORA-01110: data file 9: 'D:\ORACLE64\ORADATA\ORA817\HRPRUN_DATA05.DBF'
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_5009\ora817_p000_5472_i5009.trc
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_p000_5472.trc  (incident=5010):
ORA-01578: ORACLE data block corrupted (file # , block # )
Errors in file D:\ORACLE64\diag\rdbms\ora817\ora817\trace\ora817_smon_7424.trc  (incident=4962):
ORA-01578: ORACLE data block corrupted (file # 9, block # 504643)
ORA-01110: data file 9: 'D:\ORACLE64\ORADATA\ORA817\HRPRUN_DATA05.DBF'
Incident details in: D:\ORACLE64\diag\rdbms\ora817\ora817\incident\incdir_5010\ora817_p000_5472_i5010.trc

这次就比较清晰了,数据库在open过程中由于smon启动了并行回滚并遇到了坏块,导致P091进程和smon进程错误。因为数据库已经open,这个坏块导致无法回滚,直接对这个对象进行处理即可解决掉这个回滚报错问题.