12c中alert log的时间格式

从12.2.0.1开始，oracle日志中默认的时间格式做了调整，会看到时间变成了统一的具有毫秒精度的格式

PDB$SEED(2):Endian type of dictionary set to little
PDB$SEED(2):Undo initialization finished serial:0 start:144555510 end:144555510 diff:0 ms (0.0 seconds)
PDB$SEED(2):Database Characterset for PDB$SEED is AL32UTF8
2018-11-28T14:25:19.056231+08:00
PDB$SEED(2):Opatch validation is skipped for PDB PDB$SEED (con_id=0)
2018-11-28T14:25:19.722898+08:00
PDB$SEED(2):Opening pdb with no Resource Manager plan active
2018-11-28T14:25:21.006576+08:00
Starting background process CJQ0
Completed: ALTER DATABASE OPEN

12.2.0.1之前的样式

Fri Aug 24 10:41:46 2018
MMNL started with pid=16, OS id=12084
starting up 1 shared server(s) ...
ORACLE_BASE from environment = /u01/app/oracle
Fri Aug 24 10:41:46 2018
ALTER DATABASE   MOUNT
Changing di2dbun from  to xb
Successful mount of redo thread 1, with mount id 2904689898
Database mounted in Exclusive Mode
Lost write protection disabled
Completed: ALTER DATABASE   MOUNT
Fri Aug 24 10:41:50 2018
ALTER DATABASE OPEN

这是由于从12.2.0.1开始引入了新的参数UNIFORM_LOG_TIMESTAMP_FORMAT,这个参数默认是true，即表示oracle中所有的trc文件和log file文件（例如alert log）默认会使用新的时间格式，如果看不习惯可以修改回去

SYS@ora12c> alter system set UNIFORM_LOG_TIMESTAMP_FORMAT=FALSE scope=both;

System altered.

SYS@ora12c> alter system switch logfile;

System altered.

重新查看日志

ALTER SYSTEM SET uniform_log_timestamp_format=FALSE SCOPE=BOTH;
Wed Nov 28 14:39:45 2018
Thread 1 advanced to log sequence 4 (LGWR switch)