Search notes:

Oracle SQL: ALTER DATABASE

Oracle apparently considers alter database to be a DDL statement.

alter database add standby logfile

alter database add standby logfile ('/path/to/file') size 500M;
alter database add standby logfile thread 2 size 500M;

alter database convert to physical standby

Converts a snapshot standby database to a physical standby database.
The database must be mounted, but not open.
It must have been mounted at least once in read-write mode.

alter database disable thread n

alter database drop logfile group n

alter database force logging

Forced logging prevents unlogged direct writes in a database.
The statement might take a bit of time to complete because it has to wait until all unlogged direct write I/O is flushed.
A primary database in a data guard environment must be running with forced logging.

alter database open …

Upgrade/migrate mode

The database can be opened in the very limited upgrade/migrate mode (which lacks package standard and dbms_output, among other things). 
alter database open upgrade

alter database register logfile

alter database register logfile '/path/to/some/possibly/archived/logfile.arc';

alter database recover managed standby database

Enable Real-Time Apply on physical standby databases.
Compare with alter database start logical standby apply immediate 
alter database recover managed standby database;

cancel

Stop application of Redo Apply on the physical standby DB. 
alter database recover managed standby database cancel;

disconnect

Without using disconnect, a foreground session is started, that is, the session cannot be used to execute further SQL statements. With disconnect, a background session is started: 
alter database recover managed standby database ~disconnect~;

alter database start logical standby apply immediate

Enable Real-Time Apply on logical standby databases.
Compare with alter database recover managed standby database

TODO

alter database open upgrade

Apparently, there is also an alter database open upgrade (See $ORACLE_HOME/rdbms/admin/dbms_registry_basic.sql].
This clause puts the database in the (limited) upgrade/migrate mode in which the some functionality is missing, such as dbms_output etc.

alter database property set

alter database property set upgrade_pdb_on_open='true';
See also props$ and $ORACLE_HOME/rdbms/admin/catappcontainer.sql

See also

alter database archivelog
alter database database
Compare alter database with alter system and alter session.

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/developm...', 1788383112, '216.73.217.21', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/development/databases/Oracle/SQL/statement/nouns/database/alter/index(139): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78