Oracle:

ALTER SYSTEM

ALTER SYSTEM
{ archive_log_clause
| checkpoint_clause
| check_datafiles_clause
| distributed_recov_clauses
| FLUSH { SHARED_POOL | GLOBAL CONTEXT | BUFFER_CACHE
| REDO TO target_db_name [ [ NO ] CONFIRM APPLY ] }
| end_session_clauses
| SWITCH LOGFILE
| { SUSPEND | RESUME }
| quiesce_clauses
| rolling_migration_clauses
| security_clauses
| shutdown_dispatcher_clause
| REGISTER
| SET alter_system_set_clause
[ alter_system_set_clause ]...
| RESET alter_system_reset_clause
[ alter_system_reset_clause ]...
} ;

checkpoint_clause::=
CHECKPOINT [ GLOBAL | LOCAL ]
check_datafiles_clause::=
CHECK DATAFILES [ GLOBAL | LOCAL ]
distributed_recov_clauses::=
{ ENABLE | DISABLE } DISTRIBUTED RECOVERY
end_session_clauses::=
{ DISCONNECT SESSION 'integer1, integer2'
[ POST_TRANSACTION ]
| KILL SESSION 'integer1, integer2 [, @integer3]'
}
[ IMMEDIATE ]
quiesce_clauses::=
QUIESCE RESTRICTED | UNQUIESCE
rolling_migration_clauses::=
{ START ROLLING MIGRATION TO 'ASM_version'
| STOP ROLLING MIGRATION
}
security_clauses::=
{ { ENABLE | DISABLE } RESTRICTED SESSION
| SET ENCRYPTION WALLET OPEN IDENTIFIED BY
{ "wallet_password" | "HSM_auth_string" }
| SET ENCRYPTION WALLET CLOSE
[ IDENTIFIED BY { "wallet_password" | "HSM_auth_string" } ]
| "set_encryption_key"
}
set_encryption_key::=
{ SET ENCRYPTION KEY
{
[ "certificate_id" ] IDENTIFIED BY "wallet_password"
|
IDENTIFIED BY "HSM_auth_string" [ MIGRATE USING "wallet_password" ]
}
}
shutdown_dispatcher_clause::=
SHUTDOWN [ IMMEDIATE ] dispatcher_name
alter_system_set_clause::=
{ set_parameter_clause
| USE_STORED_OUTLINES = (TRUE | FALSE | category_name)
| GLOBAL_TOPIC_ENABLED = (TRUE | FALSE)
}
set_parameter_clause::=
parameter_name =
parameter_value [, parameter_value ]...
[ COMMENT = string ]
[ DEFERRED ]
[ { SCOPE = { MEMORY | SPFILE | BOTH }
| SID = { 'sid' | '*' }
}...
]
alter_system_reset_clause::=
parameter_name
[ { SCOPE = SPFILE
| SID = { 'sid' | '*' }
}...
]

Example

ALTER SYSTEM ARCHIVE LOG CHANGE 9356083;

ALTER SYSTEM ARCHIVE LOG
LOGFILE 'diskl:log6.log'
TO 'diska:[arch$]';

ALTER SYSTEM SET QUERY_REWRITE_ENABLED = TRUE;

ALTER SYSTEM
ENABLE RESTRICTED SESSION;

ALTER SYSTEM
DISABLE RESTRICTED SESSION;

ALTER SYSTEM SET ENCRYPTION WALLET OPEN IDENTIFIED BY "password";
ALTER SYSTEM SET ENCRYPTION KEY IDENTIFIED BY "password";

ALTER SYSTEM SET ENCRYPTION WALLET CLOSE IDENTIFIED BY "password";

ALTER SYSTEM SET ENCRYPTION WALLET CLOSE;

ALTER SYSTEM FLUSH SHARED_POOL;

ALTER SYSTEM CHECKPOINT;

ALTER SYSTEM SET RESOURCE_LIMIT = TRUE;

ALTER SYSTEM SET SHARED_SERVERS = 25;

ALTER SYSTEM
SET DISPATCHERS =
'(INDEX=0)(PROTOCOL=TCP)(DISPATCHERS=5)',
'(INDEX=1)(PROTOCOL=ipc)(DISPATCHERS=10)';

ALTER SYSTEM
SET LICENSE_MAX_SESSIONS = 64
LICENSE_SESSIONS_WARNING = 54;

ALTER SYSTEM SET LICENSE_MAX_SESSIONS = 0;

ALTER SYSTEM SET LICENSE_MAX_USERS = 200;

ALTER SYSTEM SWITCH LOGFILE;

ALTER SYSTEM ENABLE DISTRIBUTED RECOVERY;

ALTER SYSTEM DISABLE DISTRIBUTED RECOVERY;

ALTER SYSTEM KILL SESSION '39, 23';

ALTER SYSTEM DISCONNECT SESSION '13, 8' POST_TRANSACTION;