今天在设置 alter system set log_checkpoints_to_alert=true; 这个参数时，第一时间在alert日志中看到了该参数的修改记录，默认范围就是both。虽然知道这个知识点，当该参数设置成功后在tail alert日志的窗口第一时间看到这个输出还是挺有意思的。
SYS@OCM10G >show parameter log_checkpoint
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
log_checkpoint_interval integer 0
log_checkpoint_timeout integer 1800
log_checkpoints_to_alert boolean FALSE
SYS@OCM10G >alter system set log_checkpoints_to_alert=true;
System altered.
tail 日志片段
Completed: ALTER DATABASE OPEN
Tue Dec 23 21:48:33 2014
db_recovery_file_dest_size of 200 MB is 34.10% used. This is a
user-specified limit on the amount of space that will be used by this
database for recovery-related files, and does not reflect the amount of
space available in the underlying filesystem or ASM diskgroup.
Tue Dec 23 21:54:31 2014
Shutting down archive processes
Tue Dec 23 21:54:36 2014
ARCH shutting down
ARC2: Archival stoppedWed Dec 24 20:53:56 2014
MMNL absent for 81271 secs; Foregrounds taking over
Wed Dec 24 20:55:12 2014
ALTER SYSTEM SET log_checkpoints_to_alert=TRUE SCOPE=BOTH;
下图是官方文档对该参数的解释，截图做个纪念
LOG_CHECKPOINTS_TO_ALERT
|
Property
|
Description
|
|
Parameter type
|
Boolean
|
|
Default value
|
false
|
|
Modifiable
|
ALTER SYSTEM
|
|
Range of values
|
true | false
|
|
Basic
|
No
|
LOG_CHECKPOINTS_TO_ALERT lets you log your checkpoints to the alert file. Doing so is useful for determining whether checkpoints are occurring at the desired frequency.
该参数用来检测checkpoints的发生频率
一个寻常的操作证实了alter system 默认范围为both
原文：http://blog.itpub.net/29047826/viewspace-1379043/
