作者：沈光宇

爱可生南区 DBA 团队成员，次要负责 MySQL 故障解决和性能优化。对技术执着，为客户负责。

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一、背景

某客户MySQL实例中数据较大(上T的数据量)，须要将MySQL中数据全量/增量疾速迁徙至DBLE。TiDB DM反对多线程数据导出导入及增量同步，因而抉择了TiDB DM为作数据迁徙工具。本文以此案例为背景，介绍应用TiDB DM将数据从MySQL迁徙至DBLE的办法及遇到的一些问题。

二、数据迁徙示意图及服务器环境

（1）数据迁徙示意图如下：

（2）服务器环境如下:

服务器IP角色端口版本备注
10.186.65.83dm master8261/8291V2.0.7tiup装置节点
10.186.65.118dm worker8262V2.0.7
10.186.65.14SRC MySQL4490MySQL 8.0.18
10.186.65.4DBLE8066DBLE 3.21.10.6
10.186.65.61DBLE datanode4408MySQL 8.0.25
10.186.65.65DBLE datanode4408MySQL 8.0.25

三、装置 TiDB DM

（1）筹备环境及装置 tiup

#别离在dm master和worker节点主机创立tidb用户,明码为dmadmin,并配置sudoshell> useradd tidbshell> echo "dmadmin" | passwd tidb --stdinshell> echo "tidb ALL=(ALL) NOPASSWD: ALL" > /etc/sudoers.d/tidb#切换至tidb用户,生成密钥，并做ssh信赖,dm集群内机器都须要做ssh信赖shell> su - tidbshell> ssh-keygen -t rsashell> ssh-copy-id -i ~/.ssh/id_rsa.pub tidb@10.186.65.118shell> ssh-copy-id -i ~/.ssh/id_rsa.pub tidb@10.186.65.83#装置tiup,在tidb用户下shell> curl --proto '=https' --tlsv1.2 -sSf https://tiup-mirrors.pingcap.com/install.sh | shshell> source .bash_profileshell> which tiup~/.tiup/bin/tiup#装置dmctlshell> tiup install dm dmctl:v2.0.7component dm version v1.10.2 is already installeddownload https://tiup-mirrors.pingcap.com/dmctl-v2.0.7-linux-amd64.tar.gz 26.92 MiB / 26.92 MiB 100.00% 10.01 MiB/s

（2）装置dm-cluster

#生成配置模版shell> tiup dm template > dm_topology.yaml#批改后配置文件如下：shell> cat dm_topology.yaml  |grep -v ^[#-] |grep -v ^$global:  user: "tidb"  ssh_port: 22  deploy_dir: "/home/tidb/dm/deploy"  data_dir: "/home/tidb/dm/data"master_servers:  - host: 10.186.65.83worker_servers:  - host: 10.186.65.118monitoring_servers:  - host: 10.186.65.83grafana_servers:  - host: 10.186.65.83alertmanager_servers:  - host: 10.186.65.83  #装置、并启动DM集群shell> tiup dm deploy dm-test v2.0.7 ./dm_topology.yaml --user tidb -i /home/tidb/.ssh/id_rsashell> tiup dm start dm-test#查看DM集群[tidb@10_186_65_83 ~]$ tiup dm display dm-testtiup is checking updates for component dm ...Starting component `dm`: /home/tidb/.tiup/components/dm/v1.10.2/tiup-dm display dm-testCluster type:       dmCluster name:       dm-testCluster version:    v2.0.7Deploy user:        tidbSSH type:           builtinGrafana URL:        http://10.186.65.83:3000ID                  Role          Host           Ports      OS/Arch       Status     Data Dir                              Deploy Dir--                  ----          ----           -----      -------       ------     --------                              ----------10.186.65.83:9093   alertmanager  10.186.65.83   9093/9094  linux/x86_64  Up         /home/tidb/dm/data/alertmanager-9093  /home/tidb/dm/deploy/alertmanager-909310.186.65.83:8261   dm-master     10.186.65.83   8261/8291  linux/x86_64  Healthy|L  /home/tidb/dm/data/dm-master-8261     /home/tidb/dm/deploy/dm-master-826110.186.65.118:8262  dm-worker     10.186.65.118  8262       linux/x86_64  Free       /home/tidb/dm/data/dm-worker-8262     /home/tidb/dm/deploy/dm-worker-826210.186.65.83:3000   grafana       10.186.65.83   3000       linux/x86_64  Up         -                                     /home/tidb/dm/deploy/grafana-300010.186.65.83:9090   prometheus    10.186.65.83   9090       linux/x86_64  Up         /home/tidb/dm/data/prometheus-9090    /home/tidb/dm/deploy/prometheus-9090Total nodes: 5

四、DBLE端配置

（1）db.xml

<?xml version="1.0"?><dble:db xmlns:dble="http://dble.cloud/">    <dbGroup name="dbGroup1" rwSplitMode="0" delayThreshold="-1">        <heartbeat>select 1</heartbeat>        <dbInstance name="host_1" url="10.186.65.61:4408" user="sgy" password="QfnHoIeIYL7ZT+EdJMYNuiLw6glbx2hEyrqxK+uxFPU8vja8vZHCLEKvKBOt1vOJdXCCgW7wNidJaTYWORDaUg==" maxCon="2000" minCon="50" primary="true"  usingDecrypt="true"></dbInstance>    </dbGroup>    <dbGroup name="dbGroup2" rwSplitMode="0" delayThreshold="-1">        <heartbeat>select 1</heartbeat>        <dbInstance name="host_2" url="10.186.65.65:4408" user="sgy" password="d+rG/82+4h21ARS8D6Gu5MIFQ2UBC0h+ZS0EI7bvWAtTJUBsKuFY8+AVZtW1pZk+qtISoI2WpVt29Z9eqMRP5A==" maxCon="2000" minCon="50" primary="true"  usingDecrypt="true"></dbInstance>    </dbGroup></dble:db>#注：用户明码为加密后的字符串

（2）sharding.xml

<?xml version="1.0"?><dble:sharding xmlns:dble="http://dble.cloud/" >    <schema name="dm_meta" sqlMaxLimit="-1">        <singleTable name="mysql_sync_to_dble_loader_checkpoint" shardingNode="dm_meta" />        <singleTable name="mysql_sync_to_dble_syncer_checkpoint" shardingNode="dm_meta" />    </schema>    <schema name="sbtest" sqlMaxLimit="-1">        <shardingTable name="sbtest1" shardingNode="dn1,dn2,dn3,dn4" sqlMaxLimit="-1" shardingColumn="id" function="pro_func_jumpHash"></shardingTable>        <shardingTable name="sbtest2" shardingNode="dn1,dn2,dn3,dn4" sqlMaxLimit="-1" shardingColumn="id" function="pro_func_jumpHash"></shardingTable>        <shardingTable name="t1" shardingNode="dn1,dn2,dn3,dn4" sqlMaxLimit="-1" shardingColumn="c1" function="pro_func_jumpHash"></shardingTable>        <shardingTable name="t2" shardingNode="dn1,dn2,dn3,dn4" sqlMaxLimit="-1" shardingColumn="c1" function="pro_func_jumpHash"></shardingTable>    </schema>    <shardingNode name="dn1" dbGroup="dbGroup1" database="dh_dn1"></shardingNode>    <shardingNode name="dn2" dbGroup="dbGroup1" database="dh_dn2"></shardingNode>     <shardingNode name="dn3" dbGroup="dbGroup2" database="dh_dn3"></shardingNode>    <shardingNode name="dn4" dbGroup="dbGroup2" database="dh_dn4"></shardingNode>    <shardingNode name="dm_meta" dbGroup="dbGroup1" database="dm_meta"/>        <function name="pro_func_jumpHash" class="jumpStringHash">        <property name="partitionCount">4</property>        <property name="hashSlice">0:0</property>    </function></dble:sharding>注：须要提前配置好DM同步时保留数据的schema及两张表,表名别离是dm同步工作名 + _loader_checkpoint 即表mysql_sync_to_dble_loader_checkpointdm同步工作名 + _syncer_checkpoint 即表mysql_sync_to_dble_syncer_checkpoint

（3）user.xml

<?xml version="1.0"?><dble:user xmlns:dble="http://dble.cloud/">    <managerUser name="root" password="RYQdYYnzbcZlDuhV4LhJxFTM8kbU3d0y183LU+FgRWzNscvvvFPcdmeEKMdswMyzIaA+kObcozliHEYAlT0AjA==" usingDecrypt="true"></managerUser>    <shardingUser name="sz" schemas="sbtest,dm_meta" password="jyaXmGFU+mdTGbUZIVbdEcVwItLPI+Yjxdq4wkOzhAYRB29WGZJd0/PkTJh3ky/v4E2yYoqgUzJXPzPRPiQF0Q==" usingDecrypt="true" readOnly="false" maxCon="1000"></shardingUser></dble:user>#注：用户明码为加密后的字符串

（4）登陆 DBLE 治理端执行创立物理数据库命令

shell> /data/mysql/base/5.7.36/bin/mysql -uroot -padmin -h 10.186.65.4 -P 9066dble> create database @@shardingNode = 'dn$1-4';Query OK, 1 row affected (0.06 sec)dble> create database @@shardingNode = 'dm_meta';Query OK, 1 row affected (0.01 sec)

五、在源端 MySQL 压测创立测试数据

#执行prepare，初始化100W行数据 /usr/share/sysbench/oltp_insert.lua --mysql-db=sbtest --mysql-host=10.186.65.14 --mysql-port=4490  --mysql-user=sgy --mysql-password=admin  --tables=2 --table-size=1000000 --threads=16 --time=60 --report-interval=1 --max-requests=0 --percentile=95 --mysql-ignore-errors=1062   preparesysbench 1.0.17 (using system LuaJIT 2.0.4)Initializing worker threads...Creating table 'sbtest1'...Creating table 'sbtest2'...Inserting 1000000 records into 'sbtest2'Inserting 1000000 records into 'sbtest1'Creating a secondary index on 'sbtest2'...Creating a secondary index on 'sbtest1'...#利用sysbench一直写入数据shell> /usr/share/sysbench/oltp_read_write.lua --mysql-db=sbtest --mysql-host=10.186.65.14 --mysql-port=4490  --mysql-user=sgy --mysql-password=admin  --tables=2 --table-size=2000000 --threads=16 --time=6000 --report-interval=1 --max-requests=0 --percentile=95 --mysql-ignore-errors=1062   runsysbench 1.0.17 (using system LuaJIT 2.0.4)Running the test with following options:Number of threads: 16Report intermediate results every 1 second(s)Initializing random number generator from current timeInitializing worker threads...Threads started![ 1s ] thds: 16 tps: 585.44 qps: 11916.49 (r/w/o: 8360.33/1282.63/2273.53) lat (ms,95%): 55.82 err/s: 0.00 reconn/s: 0.00[ 2s ] thds: 16 tps: 744.18 qps: 14819.02 (r/w/o: 10379.16/1609.36/2830.50) lat (ms,95%): 41.85 err/s: 0.00 reconn/s: 0.00[ 3s ] thds: 16 tps: 605.11 qps: 12144.20 (r/w/o: 8500.54/1321.24/2322.42) lat (ms,95%): 47.47 err/s: 0.00 reconn/s: 0.00[ 4s ] thds: 16 tps: 773.91 qps: 15558.16 (r/w/o: 10881.71/1737.79/2938.65) lat (ms,95%): 41.10 err/s: 0.00 reconn/s: 0.00

六、启动数据同步工作

（1）配置数据源

#应用dmctl工具生成明码加密字符串,每次执行都会产生不同的加密字符串shell> tiup dmctl encrypt 'admin'dmXgktpuF18RP1mDN/B2UkA6pDN9PQ==#mysql数据库配置文件如下shell> cat mysql_source_14_4490.yamlsource-id: "mysql_source_14_4490"from:  host: "10.186.65.14"  port: 4490  user: "sgy"  password: "dmXgktpuF18RP1mDN/B2UkA6pDN9PQ=="  #创立数据源shell> tiup dmctl --master-addr 10.186.65.83:8261  operate-source create ./mysql_source_14_4490.yamlStarting component `dmctl`: /home/tidb/.tiup/components/dmctl/v2.0.7/dmctl/dmctl --master-addr 10.186.65.83:8261 operate-source create ./mysql_source_14_4490.yaml{    "result": true,    "msg": "",    "sources": [        {            "result": true,            "msg": "",            "source": "mysql_source_14_4490",            "worker": "dm-10.186.65.118-8262"        }    ]}#查看数据源shell> tiup dmctl --master-addr 10.186.65.83:8261  operate-source show{    "result": true,    "msg": "",    "sources": [        {            "result": true,            "msg": "",            "source": "mysql_source_14_4490",            "worker": "dm-10.186.65.118-8262"        }    ]}

（2）配置同步工作

#同步配置文件如下shell> cat mysql_sync_to_dble.yamlname: "mysql_sync_to_dble"      #同步工作名task-mode: "all"                #全量 + Binlog 实时同步clean-dump-file: truetimezone: "Asia/Shanghai"ignore-checking-items: ["auto_increment_ID"]target-database:  host: "10.186.65.4"           #DBLE主机IP地址  port: 8066                    #DBLE流量端口  user: "sz"                    #连贯DBLE的用户  password: "KRfSNtdxe63tehpnCYoCz0ABdUGivg=="    #连贯DBLE用户明码，用tiup dmctl encrypt 'password'生成mysql-instances:-  source-id: "mysql_source_14_4490"  block-allow-list: "global"  mydumper-config-name: "global"  loader-config-name:   "global"  syncer-config-name: "global"block-allow-list:  global:    do-dbs: ["sbtest"]            #只迁徙sbtest库mydumpers:  global:    extra-args: "-B sbtest"      #只dump sbtest库loaders:  global:    pool-size: 8syncers:  global:    worker-count: 8#更具体配置阐明参考官网文档：https://docs.pingcap.com/zh/tidb-data-migration/v2.0/task-configuration-file-full#%E5%AE%8C%E6%95%B4%E9%85%8D%E7%BD%AE%E6%96%87%E4%BB%B6%E7%A4%BA%E4%BE%8B#查看配置文件shell> tiup dmctl:v2.0.7 --master-addr=10.186.65.83:8261  check-task ./mysql_sync_to_dble.yamlStarting component `dmctl`: /home/tidb/.tiup/components/dmctl/v2.0.7/dmctl/dmctl --master-addr=10.186.65.83:8261 check-task ./mysql_sync_to_dble.yaml{    "result": true,    "msg": "check pass!!!"}#启动同步工作shell> tiup dmctl:v2.0.7 --master-addr=10.186.65.83:8261  start-task ./mysql_sync_to_dble.yamlStarting component `dmctl`: /home/tidb/.tiup/components/dmctl/v2.0.7/dmctl/dmctl --master-addr=10.186.65.83:8261 start-task ./mysql_sync_to_dble.yaml{    "result": true,    "msg": "",    "sources": [        {            "result": true,            "msg": "",            "source": "mysql_source_14_4490",            "worker": "dm-10.186.65.118-8262"        }    ]}#在dm-worker节点查看导出的SQL文件, shell> ls -lh /home/tidb/dm/deploy/dm-worker-8262/dumped_data.mysql_sync_to_dbletotal 384M-rw-r--r-- 1 tidb tidb 187 Aug  5 14:04 metadata-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest1.0000000000000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest1.0000000010000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest1.0000000020000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest1.0000000030000.sql-rw-r--r-- 1 tidb tidb 369 Aug  5 14:04 sbtest.sbtest1-schema.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest2.0000000000000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest2.0000000010000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest2.0000000020000.sql-rw-r--r-- 1 tidb tidb 48M Aug  5 14:04 sbtest.sbtest2.0000000030000.sql-rw-r--r-- 1 tidb tidb 369 Aug  5 14:04 sbtest.sbtest2-schema.sql-rw-r--r-- 1 tidb tidb 152 Aug  5 14:04 sbtest-schema-create.sql#创立库SQL文件shell> head /home/tidb/dm/deploy/dm-worker-8262/dumped_data.mysql_sync_to_dble/sbtest-schema-create.sql/*!40101 SET NAMES binary*/;CREATE DATABASE `sbtest` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_bin */ /*!80016 DEFAULT ENCRYPTION='N' */;#创立表SQL文件shell> head /home/tidb/dm/deploy/dm-worker-8262/dumped_data.mysql_sync_to_dble/sbtest.sbtest1-schema.sql/*!40101 SET NAMES binary*/;CREATE TABLE `sbtest1` (  `id` int(11) NOT NULL AUTO_INCREMENT,  `k` int(11) NOT NULL DEFAULT '0',  `c` char(120) COLLATE utf8mb4_bin NOT NULL DEFAULT '',  `pad` char(60) COLLATE utf8mb4_bin NOT NULL DEFAULT '',  PRIMARY KEY (`id`),  KEY `k_1` (`k`)) ENGINE=InnoDB AUTO_INCREMENT=1000001 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;#dump生成批量插入数据SQL文件shell> head /home/tidb/dm/deploy/dm-worker-8262/dumped_data.mysql_sync_to_dble/sbtest.sbtest1.0000000000000.sql/*!40101 SET NAMES binary*/;INSERT INTO `sbtest1` (`id`,`k`,`c`,`pad`) VALUES(1,498670,'31451373586-15688153734-79729593694-96509299839-83724898275-86711833539-78981337422-35049690573-51724173961-87474696253','98996621624-36689827414-04092488557-09587706818-65008859162'),(2,497778,'21472970079-70972780322-70018558993-71769650003-09270326047-32417012031-10768856803-14235120402-93989080412-18690312264','04776826683-45880822084-77922711547-29057964468-76514263618'),(3,498956,'49376827441-24903985029-56844662308-79012577859-40518387141-60588419212-24399130405-42612257832-29494881732-71506024440','26843035807-96849339132-53943793991-69741192222-48634174017'),(4,518727,'85762858421-36258200885-10758669419-44272723583-12529521893-95630803635-53907705724-07005352902-43001596772-53048338959','37979424284-37912826784-31868864947-42903702727-96097885121'),(5,502480,'24805466175-85245528617-94635882649-46305216925-28637832581-03224489581-68883711727-95491561683-91969681472-12022277774','19288959552-55556468076-14192290426-55457672510-18043372364'),(6,500774,'52892836230-54177743992-01821871718-48412537487-30066596248-87215430797-00375777469-64498831720-58542556455-90784765418','59487960480-08453890592-99628797439-16757639138-29377916560'),(7,501466,'85820931248-14475640036-11980694501-86588543167-31029306229-09626867980-90685354565-02350460358-25863585366-53793794448','26081374730-86321700986-51212137094-30635959762-03880194434'),(8,497838,'81578049255-33453976301-67096870761-27658738403-30546242249-53677469854-26594573136-34292002037-52736825353-99165193170','64289062455-51067794311-09919261228-11533354367-07401173317'),

（3）查看同步工作状态

shell> tiup dmctl:v2.0.7 --master-addr=10.186.65.83:8261  query-status ./mysql_sync_to_dble.yamlStarting component `dmctl`: /home/tidb/.tiup/components/dmctl/v2.0.7/dmctl/dmctl --master-addr=10.186.65.83:8261 query-status ./mysql_sync_to_dble.yaml{    "result": true,    "msg": "",    "sources": [        {            "result": true,            "msg": "",            "sourceStatus": {                "source": "mysql_source_14_4490",                "worker": "dm-10.186.65.118-8262",                "result": null,                "relayStatus": null            },            "subTaskStatus": [                {                    "name": "mysql_sync_to_dble",                    "stage": "Running",                    "unit": "Sync",                    "result": null,                    "unresolvedDDLLockID": "",                    "sync": {                        "totalEvents": "425355",                        "totalTps": "1203",                        "recentTps": "2386",                        "masterBinlog": "(mysql-bin.000027, 76114275)",                        "masterBinlogGtid": "c7827165-bf89-11ec-92e6-02000aba410e:1-5091258",                        "syncerBinlog": "(mysql-bin.000026, 229462770)",                        "syncerBinlogGtid": "",                        "blockingDDLs": [                        ],                        "unresolvedGroups": [                        ],                        "synced": false,                        "binlogType": "remote",                        "secondsBehindMaster": "38"                    }                }            ]        }    ]}

七、验证数据

#暂停先前执行的sysbench程序，确保dm同步与源端无提早时，对表作count(*)#在源端MySQL，对表进行count(*)mysql> select count(*) from sbtest.sbtest1;+----------+| count(*) |+----------+|  1116471 |+----------+1 row in set (0.68 sec)mysql> select count(*) from sbtest.sbtest2;+----------+| count(*) |+----------+|  1117020 |+----------+1 row in set (0.54 sec)#通过dble对表进行count(*)dble> select count(*) from sbtest.sbtest1;+----------+| count(*) |+----------+|  1116471 |+----------+1 row in set (1.04 sec)dble> select count(*) from sbtest.sbtest2;+----------+| count(*) |+----------+|  1117020 |+----------+1 row in set (1.58 sec)#在源端数据进行更新操作mysql> update sbtest.sbtest1 set c=uuid() where id=20;Query OK, 1 row affected (0.01 sec)Rows matched: 1  Changed: 1  Warnings: 0mysql> select * from sbtest.sbtest1 where id=20;+----+--------+--------------------------------------+-------------------------------------------------------------+| id | k      | c                                    | pad                                                         |+----+--------+--------------------------------------+-------------------------------------------------------------+| 20 | 501448 | 24649f0f-14d1-11ed-b4f2-02000aba410e | 91052688950-96415657187-00012408429-12357288330-41295735957 |+----+--------+--------------------------------------+-------------------------------------------------------------+1 row in set (0.00 sec)#通过dble查问数据dble> select * from sbtest.sbtest1 where id=20;+----+--------+--------------------------------------+-------------------------------------------------------------+| id | k      | c                                    | pad                                                         |+----+--------+--------------------------------------+-------------------------------------------------------------+| 20 | 501448 | 24649f0f-14d1-11ed-b4f2-02000aba410e | 91052688950-96415657187-00012408429-12357288330-41295735957 |+----+--------+--------------------------------------+-------------------------------------------------------------+1 row in set (0.01 sec)

八、注意事项

（1）TiDB DM版本要求：TiDB DM v2.0.7

（2）在进行数据量导入时须要敞开DBLE慢查问日志

#因为数据同步在全量导入阶段会产生大量慢查问，须要在执行同步工作之前先敞开DBLE的慢查问日志shell> mysql --prompt='dble>' -uroot -p -h 10.186.65.4 -P 9066#查看慢查问日志状态，1示意开启，0示意敞开dble> show @@slow_query_log;   +------------------+| @@slow_query_log |+------------------+| 1                |+------------------+1 row in set (0.00 sec) #全量数据导入前，敞开dble慢查问日志dble> disable @@slow_query_log;Query OK, 1 row affected (0.01 sec)disable slow_query_log success #待全量数据导入实现后，开启dble慢查问日志dble> enable @@slow_query_log;Query OK, 1 row affected (0.01 sec)enable slow_query_log success

（3）查看源端 MySQL 实例上是否有运行相似 pt-kill 的程序

#如果在源端MySQL实例上运行有pt-kill或相似的程序，DM同步工作在执行全量数据dump阶段，导出线程可能会被程序kill掉，导致全备失败。dm-worker.log日志如下：[ERROR] [subtask.go:311] ["unit process error"] [subtask=oms-sync-receiver] [unit=Dump] ["error information"="{\"ErrCode\":32001,\"ErrClass\":\"dump-unit\",\"ErrScope\":\"internal\",\"ErrLevel\":\"high\",\"Message\":\"mydumper/dumpling runs with error, with output (may empty): \",\"RawCause\":\"invalid connection\"}"]解决办法：先将pt-kill实用工具进行，而后再从新运行TiDM同步工作，待全量数据dump实现后在开启pt-kill。

（4）迁徙时如需对指标表表构造进行批改，如源表有建设分区而指标表通过分片后不须要建设分区、批改表字符集(倡议应用utf8mb4)等，可先将表构造从源库导出，批改后导入 DBLE 或导入 DBLE 后在批改表构造，最初再开启 DM 同步工作。

（5）源、指标表字段程序必须要统一，否则可能会导致数据不统一，两字段同为 varchar 并且长度不相等时，同步工作并不会报错，但写入指标表的值可能会被截断，如下图：

DM 工作启动后连贯指标端时，会将 session 级别 sql_mode 设置成上面值：
sql_mode='IGNORE_SPACE,NO_AUTO_VALUE_ON_ZERO,NO_ENGINE_SUBSTITUTION,ALLOW_INVALID_DATES,ONLY_FULL_GROUP_BY'；