Oracle Database: restore spfile from alert log

Today experiment, change a few system parameters, the results of the database can not be started, error:

SQL> startup
ORA-01078: failure in processing system parameters
LRM-00109: could not open parameter file '/opt/oracle/product/19c/dbhome_1/dbs/initORCLCDB.ora'

In $ORACLE_HOME/dbsnot find spfile directory, could not find pfile.
But controlfile also:

$ ls -l $ORACLE_BASE/oradata/ORCLCDB/*.ctl
-rw-r-----. 1 oracle oinstall 18759680 Feb 20 17:40 /opt/oracle/oradata/ORCLCDB/control01.ctl
-rw-r-----. 1 oracle oinstall 18759680 Feb 20 17:40 /opt/oracle/oradata/ORCLCDB/control02.ctl

In controlfile is better. Because the location of data files are here.

Thinking about recovery, refer to the article: How to Recover Lost or Missing the From the Parameter Database Files (PFILE or SPFILE .

Select restore spfile from the alert log. alert log location $ORACLE_BASE/diag/rdbms/<sid>/<sid>/trace:

$ cat /opt/oracle/diag/rdbms/orclcdb/ORCLCDB/trace/alert_ORCLCDB.log
...
  processes                = 300
  sga_max_size             = 2000M
  nls_language             = "AMERICAN"
  nls_territory            = "AMERICA"
  filesystemio_options     = "setall"
  resource_manager_plan    = "low_prio_apps"
  _exadata_feature_on      = TRUE
  sga_target               = 1500M
  control_files            = "/opt/oracle/oradata/ORCLCDB/control01.ctl"
  control_files            = "/opt/oracle/oradata/ORCLCDB/control02.ctl"
  db_block_size            = 8192
  compatible               = "19.0.0"
  db_create_file_dest      = "/opt/oracle/oradata"
  undo_tablespace          = "UNDOTBS1"
  heat_map                 = "OFF"
  inmemory_size            = 700M
  inmemory_automatic_level = "OFF"
  remote_login_passwordfile= "EXCLUSIVE"
  audit_sys_operations     = FALSE
  dispatchers              = "(PROTOCOL=TCP) (SERVICE=ORCLCDBXDB)"
  local_listener           = "LISTENER_ORCLCDB"
  audit_file_dest          = "/opt/oracle/admin/ORCLCDB/adump"
  commit_wait              = "nowait"
  commit_logging           = "batch"
  audit_trail              = "NONE"
  db_name                  = "ORCLCDB"
  open_cursors             = 300
  pga_aggregate_target     = 384M
  diagnostic_dest          = "/opt/oracle"
  enable_pluggable_database= TRUE
...

The above portion stored in a file / tmp / pfile.
then:

$ sqlplus / as sysdba
SQL> create spfile from pfile='/tmp/pfile'
SQL> startup

or:

$ sqlplus / as sysdba
SQL> startup pfile='/tmp/pfile'
SQL> create spfile from memory