read(10, "NTP0 13690\n", 64) 数据库登录缓慢

初步怀疑：下面两个參数引起：

SQL> conn / as sysdba

Connected.

SQL> show parameter lock

NAME

------------------------------------ ----------- ------------------------------

db_file_multiblock_read_count        integer     128

ddl_wait_for_locks                   boolean     FALSE

distributed_lock_timeout             integer     60

dml_locks                            integer     48420

gc_files_to_locks                    string

lock_name_space                      string

lock_sga                             boolean     TRUE

SQL> show parameter pre

NAME                                 TYPE        VALUE

os_authent_prefix                    string      ops$

pre_11g_enable_capture               boolean     FALSE

pre_page_sga                         boolean     TRUE

SQL> exit

Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bit Production

With the Partitioning, Real Application Clusters, OLAP, Data Mining

and Real Application Testing options

[oracle@KXSALE02 ~]$ tail

分析过程：

1 提取awr报告发现等待事件

Event Waits Time(s) Avg Wait(ms) % Total Call Time Wait Class

CPU time   267   103.3 

os thread startup 48 22 462 8.6 Concurrency

control file sequential read 19,523 4 0 1.7 System I/O

log file parallel write 1,322  2 1.1 System I/O

control file parallel write 1,202 3 2 1.0 System I/O

2 Dump systemstat 10 发现问题

    ---------------------------------------------------

      [80 samples,                                         12:37:56 - 12:39:16]

        idle wait at each sample

      [1 sample,                                                      12:37:55]

        waited for 'os thread startup', seq_num: 50784

          p1: ''=0x0

          p2: ''=0x0

          p3: ''=0x0

          time_waited: 0.458091 sec (sample interval: 0 sec)

时间也比較温柔

3 在測试库上开启这两个參数发现：

close(8)                                = 0 <0.000008>

close(11)                               = 0 <0.000007>

read(10, "NTP0 13690\n", 64)            = 11 <0.681689>   

fcntl(10, F_SETFD, FD_CLOEXEC)          = 0 <0.000009>

4  在查看其他生产库，假设參数不一样。基本能够确定是这两个參数引起！