ORA-01157: cannot identify/lock data file导致表空间无法on
朋友和我聊到一个案例,一个表空间本来有一个数据文件(已经有大量数据进入),然后他加入7个数据文件,这个时候他发现他加多了文件,想删除这些数据文件,可是又不怎么懂数据库,直接offline 表空间,然后rm掉相关数据文件,最后表空间无法online.我对其场景进行了模
朋友和我聊到一个案例,一个表空间本来有一个数据文件(已经有大量数据进入),然后他加入7个数据文件,这个时候他发现他加多了文件,想删除这些数据文件,可是又不怎么懂数据库,直接offline 表空间,然后rm掉相关数据文件,最后表空间无法online.我对其场景进行了模拟恢复测试,使用bbed和dul对其进行恢复
模拟场景
表空间有一个数据文件,里面有数据,然后加入一个新数据文件,进入offline tbs,然后rm数据文件
offline表空间后,该表空间存在的数据文件也会offline
SQL> create tablespace xifenfei datafile
2 '/u01/oracle/ora9i/oradata/xifenfei01.dbf' size 10M autoextend on next 16M;
Tablespace created.
SQL> create table chf.t_xifenfei01 tablespace xifenfei
2 as select * from dba_objects;
Table created.
SQL> create table chf.t_xifenfei02 tablespace xifenfei
2 as select * from dba_tables;
Table created.
SQL> SELECT COUNT(*) FROM CHF.T_XIFENFEI01;
COUNT(*)
----------
30758
SQL> C/01/02
1* SELECT COUNT(*) FROM CHF.T_XIFENFEI02
SQL> /
COUNT(*)
----------
865
SQL> select tablespace_name,segment_name from dba_segments
2 where segment_name like 'T_XIFENFEI%';
TABLESPACE_NAME SEGMENT_NAME
------------------------------ -------------------------
XIFENFEI T_XIFENFEI01
XIFENFEI T_XIFENFEI02
SQL> ALTER tablespace xifenfei add datafile
2 '/u01/oracle/ora9i/oradata/xifenfei02.dbf' size 16m;
Tablespace altered.
SQL> alter tablespace xifenfei offline;
Tablespace altered.
SQL> select file#,status$ from file$;
FILE# STATUS$
---------- ----------
1 2
2 2
3 2
4 2
5 2
6 2
7 2
8 2
9 2
10 2
11 2
12 2
12 rows selected.
SQL> set pages 1000
SQL> /
FILE# STATUS$
---------- ----------
1 2
2 2
3 2
4 2
5 2
6 2
7 2
8 2
9 2
10 2
11 2
12 2
12 rows selected.
SQL> select file#,status from v$datafile;
FILE# STATUS
---------- -------
1 SYSTEM
2 ONLINE
3 ONLINE
4 ONLINE
5 ONLINE
6 ONLINE
7 ONLINE
8 ONLINE
9 ONLINE
10 ONLINE
11 OFFLINE
12 OFFLINE
12 rows selected.
SQL> select file#,status from v$datafile_header;
FILE# STATUS
---------- -------
1 ONLINE
2 ONLINE
3 ONLINE
4 ONLINE
5 ONLINE
6 ONLINE
7 ONLINE
8 ONLINE
9 ONLINE
10 ONLINE
11 OFFLINE
12 OFFLINE
12 rows selected.
SQL> select tablespace_name,status from dba_tablespaces;
TABLESPACE_NAME STATUS
------------------------------ ---------
SYSTEM ONLINE
UNDOTBS1 ONLINE
TEMP ONLINE
CWMLITE ONLINE
DRSYS ONLINE
EXAMPLE ONLINE
INDX ONLINE
ODM ONLINE
TOOLS ONLINE
USERS ONLINE
XDB ONLINE
XIFENFEI OFFLINE
12 rows selected.
SQL> select ts#,name,online$ from ts$;
TS# NAME ONLINE$
---------- ------------------------------ ----------
0 SYSTEM 1
1 UNDOTBS1 1
2 TEMP 1
3 CWMLITE 1
4 DRSYS 1
5 EXAMPLE 1
6 INDX 1
7 ODM 1
8 TOOLS 1
9 USERS 1
10 XDB 1
11 UNDOTBS2 3
12 XIFENFEI 2
13 rows selected.
SQL> col name for a50
SQL> select file#,name from v$datafile;
FILE# NAME
---------- --------------------------------------------------
1 /u01/oracle/ora9i/oradata/ora9i/system01.dbf
2 /u01/oracle/ora9i/oradata/ora9i/undotbs01.dbf
3 /u01/oracle/ora9i/oradata/ora9i/cwmlite01.dbf
4 /u01/oracle/ora9i/oradata/ora9i/drsys01.dbf
5 /u01/oracle/ora9i/oradata/ora9i/example01.dbf
6 /u01/oracle/ora9i/oradata/ora9i/indx01.dbf
7 /u01/oracle/ora9i/oradata/ora9i/odm01.dbf
8 /u01/oracle/ora9i/oradata/ora9i/tools01.dbf
9 /u01/oracle/ora9i/oradata/ora9i/users01.dbf
10 /u01/oracle/ora9i/oradata/ora9i/xdb01.dbf
11 /u01/oracle/ora9i/oradata/xifenfei01.dbf
12 /u01/oracle/ora9i/oradata/xifenfei02.dbf
12 rows selected.
SQL> !rm /u01/oracle/ora9i/oradata/xifenfei02.dbf
SQL> !ls -l /u01/oracle/ora9i/oradata/xifenfei*
-rw-r----- 1 ora9i oinstall 10493952 Dec 25 20:19 /u01/oracle/ora9i/oradata/xifenfei01.dbf
SQL> alter tablespace xifenfei online;
alter tablespace xifenfei online
*
ERROR at line 1:
ORA-01157: cannot identify/lock data file 12 - see DBWR trace file
ORA-01110: data file 12: '/u01/oracle/ora9i/oradata/xifenfei02.dbf'
这里已经构造出来,由于由于数据文件丢失导致表空间online报ORA-01157: cannot identify/lock data file的错误
online存在数据文件
存在的数据文件online之后，表空间依然offline
SQL> alter database datafile 11 online;
Database altered.
SQL> select file#,status from v$datafile_header;
FILE# STATUS
---------- -------
1 ONLINE
2 ONLINE
3 ONLINE
4 ONLINE
5 ONLINE
6 ONLINE
7 ONLINE
8 ONLINE
9 ONLINE
10 ONLINE
11 ONLINE
12 OFFLINE
12 rows selected.
SQL> select file#,status from v$datafile;
FILE# STATUS
---------- -------
1 SYSTEM
2 ONLINE
3 ONLINE
4 ONLINE
5 ONLINE
6 ONLINE
7 ONLINE
8 ONLINE
9 ONLINE
10 ONLINE
11 ONLINE
12 OFFLINE
12 rows selected.
SQL> select tablespace_name,status from dba_tablespaces;
TABLESPACE_NAME STATUS
------------------------------ ---------
SYSTEM ONLINE
UNDOTBS1 ONLINE
TEMP ONLINE
CWMLITE ONLINE
DRSYS ONLINE
EXAMPLE ONLINE
INDX ONLINE
ODM ONLINE
TOOLS ONLINE
USERS ONLINE
XDB ONLINE
XIFENFEI OFFLINE
12 rows selected.
SQL> select ts#,name,online$ from ts$;
TS# NAME ONLINE$
---------- -------------------------------------------------- ----------
0 SYSTEM 1
1 UNDOTBS1 1
2 TEMP 1
3 CWMLITE 1
4 DRSYS 1
5 EXAMPLE 1
6 INDX 1
7 ODM 1
8 TOOLS 1
9 USERS 1
10 XDB 1
11 UNDOTBS2 3
12 XIFENFEI 2
13 rows selected.
SQL> create table chf.t_1 tablespace xifenfei
2 as select * from dual;
as select * from dual
*
ERROR at line 2:
ORA-01542: tablespace 'XIFENFEI' is offline, cannot allocate space in it
由于表空间无法online,因此对该表空间分配报ORA-01542错误
使用bbed构造数据文件欺骗数据库
[ora9i@xifenfei tmp]$ dd if=/dev/zero of=/u01/oracle/ora9i/oradata/xifenfei02.dbf
> bs=8192 count=2049
2049+0 records in
2049+0 records out
BBED> copy file 11 block 1 to file 12 block 1
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 0 to 511 Dba:0x03000001
------------------------------------------------------------------------
0b020000 0100c002 00000000 00000104 1deb0000 00002009 00000008 329bf29e
4f524139 49000000 11010000 00050000 00200000 0b000300 00000000 00000000
BBED> set count 32
COUNT 32
BBED> m /x 0c
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 280 to 311 Dba:0x03000001
------------------------------------------------------------------------
0c000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
BBED> m /x 0c
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 52 to 83 Dba:0x03000001
------------------------------------------------------------------------
0c000300 00000000 00000000 00000000 00000000 00000000 00000000 00000000
BBED> sum apply
Check value for File 12, Block 1:
current = 0xad21, required = 0xad21
SQL> alter tablespace xifenfei online;
alter tablespace xifenfei online
*
ERROR at line 1:
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: '/u01/oracle/ora9i/oradata/xifenfei02.dbf'
ORA-01251: Unknown File Header Version read for file number 12
SQL> !oerr ora 01251
01251, 00000, "Unknown File Header Version read for file number %s"
// *Cause: Read of the file header returned a record but its version cannot
// be identified. Either the header has been corrupted, or the file
// is not a valid database file.
// *Action: Have the operating system make the correct file available to
// the database, or recover the file.
BBED> m /x 01000003
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 4 to 36 Dba:0x03000001
------------------------------------------------------------------------
01000003 00000000 00000104 21ad0000 00002009 00000008 329bf29e 4f524139
BBED> sum apply
Check value for File 12, Block 1:
current = 0xace1, required = 0xace1
SQL> alter tablespace xifenfei online;
alter tablespace xifenfei online
*
ERROR at line 1:
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: '/u01/oracle/ora9i/oradata/xifenfei02.dbf'
ORA-01203: wrong incarnation of this file - wrong creation SCN
BBED> m /x 613B0300
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 100 to 131 Dba:0x03000001
------------------------------------------------------------------------
613b0300 00000000 f35bb133 f39bae33 b46c0200 00000000 00000000 00000000
BBED> sum apply
Check value for File 12, Block 1:
current = 0xa0c9, required = 0xa0c9
--提示数据文件scn比控制文件新(由于正常数据文件online过)
SQL> alter tablespace xifenfei online;
alter tablespace xifenfei online
*
ERROR at line 1:
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: '/u01/oracle/ora9i/oradata/xifenfei02.dbf'
ORA-01207: file is more recent than controlfile - old controlfile
SQL> set lines 160
SQL> col name for a50
SQL> select ts#,file#,BYTES/1024/1024/1024 status,enabled,
2 to_char(checkpoint_change#,'999999999999999') "SCN",
3 to_char(last_change#,'999999999999999')"STOP_SCN",
4 name from v$datafile;
TS# FILE# STATUS ENABLED SCN STOP_SCN NAME
----- --- ---------- ---------- -------- ------------- ---------------------------------------------
0 1 .37109375 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/system01.dbf
1 2 .1953125 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/undotbs01.dbf
3 3 .01953125 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/cwmlite01.dbf
4 4 .01953125 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/drsys01.dbf
5 5 .145874023 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/example01.dbf
6 6 .024414063 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/indx01.dbf
7 7 .01953125 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/odm01.dbf
8 8 .009765625 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/tools01.dbf
9 9 .024414063 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/users01.dbf
10 10 .043945313 READ WRITE 198231 /u01/oracle/ora9i/oradata/ora9i/xdb01.dbf
12 11 .009765625 DISABLED 228353 228353 /u01/oracle/ora9i/oradata/xifenfei01.dbf
12 12 0 DISABLED 213917 213917 /u01/oracle/ora9i/oradata/xifenfei02.dbf
12 rows selected.
SQL> set pages 100
SQL> set linesize 150
SQL> select ts#,file#,TABLESPACE_NAME,status,
2 to_char(CREATION_TIME,'yyyy-mm-dd hh24:mi:ss') CREATE_TIME,
3 to_char(checkpoint_change#,'9999999999999999') "SCN",
4 to_char(RESETLOGS_CHANGE#,'9999999999999999') "RESETLOGS SCN",FUZZY
from v$datafile_header; 5
TS# FILE# TABLESPACE_NAME STATUS CREATE_TIME SCN RESETLOGS SCN FUZ
--- ----- ---------------- ------- ------------------- --------- ----------------- ---
0 1 SYSTEM ONLINE 2004-03-10 12:17:49 198231 158900 YES
1 2 UNDOTBS1 ONLINE 2004-03-10 20:30:20 198231 158900 YES
3 3 CWMLITE ONLINE 2004-03-10 12:18:10 198231 158900 YES
4 4 DRSYS ONLINE 2004-03-10 12:18:11 198231 158900 YES
5 5 EXAMPLE ONLINE 2004-03-10 12:18:12 198231 158900 YES
6 6 INDX ONLINE 2004-03-10 12:18:16 198231 158900 YES
7 7 ODM ONLINE 2004-03-10 12:18:17 198231 158900 YES
8 8 TOOLS ONLINE 2004-03-10 12:18:19 198231 158900 YES
9 9 USERS ONLINE 2004-03-10 12:18:19 198231 158900 YES
10 10 XDB ONLINE 2004-03-10 12:18:20 198231 158900 YES
12 11 XIFENFEI OFFLINE 2014-12-25 17:57:07 228353 158900 NO
0 12 OFFLINE 0 0
12 rows selected.
BBED> m /x 9D430300
File: /u01/oracle/ora9i/oradata/xifenfei02.dbf (12)
Block: 1 Offsets: 140 to 171 Dba:0x03000001
------------------------------------------------------------------------
9d430300 00000000 f670b133 01000000 02000000 fc4e0000 10000000 02000000
BBED> SUM APPLY
Check value for File 12, Block 1:
current = 0x9982, required = 0x9982
SQL> ALTER TABLESPACE XIFENFEI ONLINE;
Tablespace altered.
在bbed的恢复过程中出现以下常见错误:
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: ‘/u01/oracle/ora9i/oradata/xifenfei02.dbf’
ORA-01251: Unknown File Header Version read for file number 12
这个主要是块号和块地址不一匹配,导致数据库无法识别
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: ‘/u01/oracle/ora9i/oradata/xifenfei02.dbf’
ORA-01203: wrong incarnation of this file – wrong creation SCN
这个由于数据文件头的创建scn和控制文件以及file$中的记录不一致
ORA-01122: database file 12 failed verification check
ORA-01110: data file 12: ‘/u01/oracle/ora9i/oradata/xifenfei02.dbf’
ORA-01207: file is more recent than controlfile – old controlfile
这个由于正常数据文件online过,或者你构造文件头使用的scn大于需要构造文件在控制文件中记录的scn值
后续处理
SQL> SELECT COUNT(*) FROM CHF.T_XIFENFEI01;
COUNT(*)
----------
30758
SQL> C/01/02
1* SELECT COUNT(*) FROM CHF.T_XIFENFEI02
SQL> /
COUNT(*)
----------
865
SQL> ALTER DATABASE DATAFILE 12 OFFLINE DROP;
Database altered.
证明通过bbed,模拟数据文件,使用完美恢复数据内容
dul恢复
SQL> ALTER TABLESPACE XIFENFEI OFFLINE;
Tablespace altered.
[ora9i@xifenfei dul]$ ./dul
Data UnLoader: 10.2.0.5.33 - Internal Only - on Thu Dec 25 21:18:54 2014
with 64-bit io functions
Copyright (c) 1994 2014 Bernard van Duijnen All rights reserved.
Strictly Oracle Internal Use Only
Within one week you will need a more recent DUL version for this os
Found db_id = 2666699570
Found db_name = ORA9I
DUL> bootstrap;
Probing file = 1, block = 417
database version 9 bootstrap$ at file 1, block 377
. unloading table BOOTSTRAP$
DUL: Warning: block number is non zero but marked deferred trying to process it anyhow
57 rows unloaded
DUL: Warning: Dictionary cache DC_BOOTSTRAP is empty
Reading BOOTSTRAP.dat 57 entries loaded
Parsing Bootstrap$ contents
Generating dict.ddl for version 9
OBJ$: segobjno 18, file 1 block 121
TAB$: segobjno 2, tabno 1, file 1 block 25
COL$: segobjno 2, tabno 5, file 1 block 25
USER$: segobjno 10, tabno 1, file 1 block 89
Running generated file "@dict.ddl" to unload the dictionary tables
. unloading table OBJ$ 31490 rows unloaded
. unloading table TAB$ 909 rows unloaded
. unloading table COL$ 35582 rows unloaded
. unloading table USER$ 63 rows unloaded
Reading USER.dat 63 entries loaded
Reading OBJ.dat 31490 entries loaded and sorted 31490 entries
Reading TAB.dat 909 entries loaded
Reading COL.dat 35582 entries loaded and sorted 35582 entries
Reading BOOTSTRAP.dat 57 entries loaded
DUL: Warning: Recreating file "dict.ddl"
Generating dict.ddl for version 9
OBJ$: segobjno 18, file 1 block 121
TAB$: segobjno 2, tabno 1, file 1 block 25
COL$: segobjno 2, tabno 5, file 1 block 25
USER$: segobjno 10, tabno 1, file 1 block 89
TABPART$: segobjno 230, file 1 block 1657
INDPART$: segobjno 234, file 1 block 1689
TABCOMPART$: segobjno 249, file 1 block 1809
INDCOMPART$: segobjno 253, file 1 block 1841
TABSUBPART$: segobjno 240, file 1 block 1737
INDSUBPART$: segobjno 245, file 1 block 1777
IND$: segobjno 2, tabno 3, file 1 block 25
ICOL$: segobjno 2, tabno 4, file 1 block 25
LOB$: segobjno 2, tabno 6, file 1 block 25
COLTYPE$: segobjno 2, tabno 7, file 1 block 25
TYPE$: segobjno 296, tabno 1, file 1 block 2129
COLLECTION$: segobjno 296, tabno 2, file 1 block 2129
ATTRIBUTE$: segobjno 296, tabno 3, file 1 block 2129
LOBFRAG$: segobjno 258, file 1 block 1881
LOBCOMPPART$: segobjno 261, file 1 block 1905
UNDO$: segobjno 15, file 1 block 105
TS$: segobjno 6, tabno 2, file 1 block 57
PROPS$: segobjno 101, file 1 block 769
Running generated file "@dict.ddl" to unload the dictionary tables
. unloading table OBJ$
DUL: Warning: Recreating file "OBJ.ctl"
31490 rows unloaded
. unloading table TAB$
DUL: Warning: Recreating file "TAB.ctl"
909 rows unloaded
. unloading table COL$
DUL: Warning: Recreating file "COL.ctl"
35582 rows unloaded
. unloading table USER$
DUL: Warning: Recreating file "USER.ctl"
63 rows unloaded
. unloading table TABPART$ 55 rows unloaded
. unloading table INDPART$ 128 rows unloaded
. unloading table TABCOMPART$ 0 rows unloaded
. unloading table INDCOMPART$ 0 rows unloaded
. unloading table TABSUBPART$ 0 rows unloaded
. unloading table INDSUBPART$ 0 rows unloaded
. unloading table IND$ 1396 rows unloaded
. unloading table ICOL$ 1842 rows unloaded
. unloading table LOB$ 427 rows unloaded
. unloading table COLTYPE$ 1160 rows unloaded
. unloading table TYPE$ 956 rows unloaded
. unloading table COLLECTION$ 250 rows unloaded
. unloading table ATTRIBUTE$ 3623 rows unloaded
. unloading table LOBFRAG$ 0 rows unloaded
. unloading table LOBCOMPPART$ 0 rows unloaded
. unloading table UNDO$ 21 rows unloaded
. unloading table TS$ 13 rows unloaded
. unloading table PROPS$ 25 rows unloaded
Reading USER.dat 63 entries loaded
Reading OBJ.dat 31490 entries loaded and sorted 31490 entries
Reading TAB.dat 909 entries loaded
Reading COL.dat 35582 entries loaded and sorted 35582 entries
Reading TABPART.dat 55 entries loaded and sorted 55 entries
Reading TABCOMPART.dat 0 entries loaded and sorted 0 entries
Reading TABSUBPART.dat 0 entries loaded and sorted 0 entries
Reading INDPART.dat 128 entries loaded and sorted 128 entries
Reading INDCOMPART.dat 0 entries loaded and sorted 0 entries
Reading INDSUBPART.dat 0 entries loaded and sorted 0 entries
Reading IND.dat 1396 entries loaded
Reading LOB.dat 427 entries loaded
Reading ICOL.dat 1842 entries loaded
Reading COLTYPE.dat 1160 entries loaded
Reading TYPE.dat 956 entries loaded
Reading ATTRIBUTE.dat 3623 entries loaded
Reading COLLECTION.dat 250 entries loaded
Reading BOOTSTRAP.dat 57 entries loaded
Reading LOBFRAG.dat 0 entries loaded and sorted 0 entries
Reading LOBCOMPPART.dat 0 entries loaded and sorted 0 entries
Reading UNDO.dat 21 entries loaded
Reading TS.dat 13 entries loaded
Reading PROPS.dat 25 entries loaded
Database character set is ZHS16GBK
Database national character set is AL16UTF16
DUL> unload table chf.t_xifenfei01;
. unloading table T_XIFENFEI01 30758 rows unloaded
DUL> unload table chf.t_xifenfei02;
. unloading table T_XIFENFEI02 865 rows unloaded
DUL>
这里证明,在表空间不能online的情况下,dul处理类似故障很轻松(但是需要重建表空间,bbed处理的从原理上可以不重建表空间),当然如果涉及的对象很多,而丢失的文件很少,可能bbed也不失为一种很不错的选择.
另外补充:如果表空间丢失的文件包含数据,也可以通过类似bbed和dul方法处理:bbed 让表空间online之后需要考虑跳过丢失文件;dul处理完全相同
- 使用 dul 挖数据文件初试
- dul 10支持oracle 11g r2
- DUL10直接支持ORACLE 8.0
- 密码保护：dul扫描磁盘抢救数据
- 密码保护：使用dul恢复asm中数据
- dul支持ORACLE 12C CDB数据库恢复
- asm disk header 彻底损坏恢复
- dul恢复truncate表测试
原文地址：ORA-01157: cannot identify/lock data file导致表空间无法on, 感谢原作者分享。
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Common problems in the Java technology stack and their solutions When developing Java applications, we often encounter some problems, such as performance issues, memory leaks, thread safety, etc. This article will introduce some common problems and their solutions, and give corresponding code examples. 1. Performance issues 1.1 Performance issues caused by frequent creation of objects Frequent creation of objects will lead to frequent triggering of garbage collection, thus affecting the performance of the program. The solution is to use object pooling or caching to reuse objects. Sample code: //Reuse objects using object pool
What are the methods of lock acquisition in Java?
May 19, 2023 pm 01:13 PM
1. The acquisition methods lock(), tryLock(), tryLock(longtime, TimeUnitunit) and lockInterruptibly() are all used to acquire locks. (1) The lock() method is the most commonly used method, which is used to obtain locks. If the lock has been acquired by another thread, wait. (2) The tryLock() method has a return value, which means it is used to try to acquire the lock. If the acquisition is successful, it returns true. If the acquisition fails (that is, the lock has been acquired by another thread), it returns false, which means this The method returns immediately no matter what. You won't be waiting there when you can't get the lock. (3) tryLoc
What is the difference between Lock and Synchronized in Java
Apr 17, 2023 pm 07:19 PM
1. From a functional point of view, Lock and Synchronized are both tools used in Java to solve thread safety issues. 2. From a feature point of view, Synchronized is the synchronization keyword in Java, Lock is the interface provided in the J.U.C package, and this The interface has many implementation classes, including the implementation of reentrant locks such as ReentrantLock. Synchronized can control the strength of the lock in two ways. One is to modify the synchronized keyword at the method level, and the other is to modify it on the code block. You can use The life cycle of the synchronized lock object is used to control the scope of the lock. The lock object is a static object or a class pair.
PHP security authentication with Auth0 Lock
Jul 24, 2023 am 11:16 AM
PHP security verification through Auth0Lock With the development of the Internet, more and more applications require user authentication and security verification to protect user privacy and data security. PHP is a widely used backend language that provides many ways to implement secure validation. Auth0 is a popular authentication and authorization platform that provides developers with a flexible and secure way to implement user authentication. Auth0Lock is one provided by Auth0
