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76 道 Oracle Goldengate 面试问题

基础
12c新特性
性能
Troubleshoot
其它

1. Oracle Goldengate 支持部署到哪些拓扑?

GoldenGate supports the following topologies. More details can be found here.

Unidirectional
Bidirectional
Peer-to-peer
Broadcast
Consolidation
Cascasding

2. Oracle Goldengate 复制链路包含哪些组件?

The replication configuration consists of the following processes.

Manager
Extract
Pump
Replicate

3. Oracle GoldenGate 支持哪些数据库?

Oracle Database
TimesTen
MySQL
IBM DB2
Microsoft SQL Server
Informix
Teradata
Sybase
Enscribe
SQL/MX

For the latest list, look here.

4. Oracle Goldengate 支持哪些事务类型的复制?

Goldengate supports both DML and DDL Replication from the source to target.

5. OGG复制中需要哪些附加日志的开关打开?

The following supplemental logging is required.

Database supplemental logging
Object level logging

6. OGG复制中为什么需要附加日志?

When a transaction is committed on the source database, only new data is written to the Redo log. However for Oracle to apply these transactions on the destination database, the before image key values are required to identify the effected rows. This data is also placed in the trail file and used to identify the rows on the destination, using the key value the transactions are executed against them.

7. 双向复制中，要考虑哪些因素?

The customer should consider the following points in an active-active replication environment.

Primary Key: Helps to identify conflicts and Resolve them.
Sequences: Are not supported. The work around is use to use odd/even, range or concatenate sequences.
Triggers: These should be disabled or suppressed to avoid using uniqueness issue
Data Looping: This can easy avoided using OGG itself
LAG: This should be minimized. If a customer says that there will not be any LAG due to network or huge load, then we don’t need to deploy CRDs. But this is not the case always as there would be some LAG and these can cause Conflicts.
CDR (Conflict Detection & Resolution): OGG has built in CDRs for all kind of DMLs that can be used to detect and resolve them.
Packaged Application: These are not supported as it may contain data types which are not support by OGG or it might not allow the application modification to work with OGG.

8. OGG 可执行程序是否支持部署在ASM Cluster File System (ACFS)?

Yes, you can install and configure OGG on ACFS.

9. OGG可执行程序是否支持部署在Database File System (DBFS)? 哪些文件可以部署在DBFS?

No, OGG binaries are not supported on DBFS. You can however store parameter files, data files (trail files), and checkpoint files on DBFS.

10. GLOBALS 文件默认的存放位置是哪?

A GLOBALS file is located under Oracle GoldenGate installation directory (OGG HOME)

11. 字段数据过滤可以在哪些进程里配置?

Filtering of the columns of a table can be set at the Extract, Pump or Replicat level.

12. OGG复制过程中，传输进程是否必须要配置?

A PUMP extract is an option, but it is highly recommended to use this to safe guard against network failures. Normally it is configured when you are setting up OGG replication across the network.

13. 经典抽取和集成集成的主要区别是什么?

经典抽取:

The Classic Capture mode is the traditional Extract process that accesses the database redo logs (optionally archive logs) to capture the DML changes occurring on the objects specified in the parameter files.
At the OS level, the GoldenGate user must be a part of the same database group which owns the database redo logs.
This capture mode is available for other RDBMS as well.
There are some data types that are not supported in Classic Capture mode.
Classic capture can’t read data from the compressed tables/tablespaces.

集成抽取 (IC):

In the Integrated Capture mode, GoldenGate works directly with the database log mining server to receive the data changes in the form of logical change records (LCRs).
IC mode does not require any special setup for the databases using ASM, transparent data encryption, or Oracle RAC.
This feature is only available for oracle databases in Version 11.2.0.3 or higher.
It also supports various object types which were previously not supported by Classic Capture.
This Capture mode supports extracting data from source databases using compression.
Integrated Capture can be configured in an online or downstream mode.

14. 列出可运行的抽取进程需要的最小参数配置?

The following are the minimium required parameters which must be defined in the extract parameter file.

EXTRACT NAME
USERID
EXTTRAIL
TABLE

15. 宏是什么?

Macro is an easier way to build your parameter file. Once a macro is written it can be called from different parameter files. Common parameters like username/password and other parameters can be included in these macros. A macro can either be another parameter file or a library.

16. 哪些地方可以调用宏?

The macros can be called from the following parameter files.

Manager
Extract
Replicat
Gobals

17. 如何定义一个宏?

A macro statement consists of the following.

Name of the Macro
Parameter list
Macro body

示例:
MACRO #macro_name
PARAMS (#param1, #param2, …)
BEGIN
< macro_body >
END;

18. 我想多个进程往一个队列文件中写入数据，是否可行?

Only one Extract process can write to one exttrail at a time. So you can’t configure multiple extracts to write to the same exttrail.

19. Oracle Goldengate可以加密哪些数据?

Oracle Goldengate provides 3 types of Encryption.

Data Encryption using Blow fish.
Password Encryption.
Network Encryption.

20. OGG提供哪些密码加密选项?

You can encrypt a password in OGG using

Blowfish algorithm and
Advance Encryption Standard (AES) algorithm

21. AES加密提供哪些加密强度?

You can encrypt the password/data using the AES in three different keys

a) 128 bit
b) 192 bit and
c) 256 bit

22. OGG是否提供相应的方法检查OGG的参数语法，而不用通过实际执行?

Yes, you can place the SHOWSYNTAX parameter in the parameter file and try starting. If there is any error you will see it.

23. 如何在解析日志时，增加缓冲大小，以保存更多交易数据?

If you are using the Classical Extract you may use the TRANSLOGOPTION ASMBUFSIZE parameter to control the read size for ASM Databases.

24. 在discard文件中，可以看到哪些信息?

When data is discarded, the discard file can contain:
1. Discard row details
2. Database Errors
3. Trail file number

25. 使用什么命令可以切换进程写一个新的队列文件?

You can use the following command to write the trail data to a new trail file.
SEND EXTRACT ext_name, ROLLOVER

26. 如何知道参数文件最近是否被修改过?

When ever a process is started, the parameters in the .prm file for the process is written to the process REPORT. You can look at the older process reports to view the parameters which were used to start up the process. By comparing the older and the current reports you can identify the changes in the parameters.

==================GoldenGate 12c关键新特性====================

27. GoldenGate 12c关键新特性有哪些?

The following are some of the more interesting features of Oracle GoldenGate 12c:

Support for Multitenant Database
Coordinated Replicat
Integrated Replicat Mode
Use of Credential store
Use of Wallet and master key
Trigger-less DDL replication
Automatically adjusts threads when RAC node failure/start
Supports RAC PDML Distributed transaction
RMAN Support for mined archive logs

28. OGG 12c安装时有哪些选项?

You can install Oracle GoldenGate 12c using in 2 ways:

1) Interactive Installation with OUI – Graphical interface
2) Silent Installation with OUI – Command Interface

29. OGG 12c中的Credential Store是什么?

OGG Crendential Store manages Encrypted Passwords and USERIDs that are used to interact with the local database and Associate them with an Alias. Instead of specifying actual USERID and Password in a command or a parameter file, you can use an alias. The Credential Store is implemented as an autologin wallet within the Oracle Credential Store Framework (CSF).

30. OGG12c如何配置Credentail Store?

Steps to configure Oracle Credential Store are as follows:

1) By Default Credential Store is is located under “dircrd” directory.
If you want to specify a different location use can specidy “CREDENTIALSTORELOCATION” parameter in GLOBALS file.
Example: CREDENTIALSTORELOCATION /u01/app/oracle/OGG_PASSWD
2) Goto OGG home and connect to GGSCI.
cd $OGG_HOME
./ggsci
GGSCI>

31. 使用什么命令创建credential store?

ADD CREDENTIALSTORE

32. 如何添加授权信息到credential store?

ALTER CREDENTIALSTORE ADD USER userid,
[PASSWORD password]
[ALIAS alias]
[DOMAIN domain]
Example: GGSCI> ALTER CREDENTIALSTORE ADD USER GGS@orcl, PASSWORD oracle ALIAS extorcl DOMAIN Oracle GoldenGate

33. 如何从Oracle Credential Store中获取信息?

GGSCI> INFO CREDENTIALSTORE
OR
GGSCI> INFO CREDENTIALSTORE DOMAIN OracleGoldenGate

34. OGG 12c中有哪些不同的数据加密方法?

In OGG 12c you can encrypt data with the following 2 methods:

1) Encrypt Data with Master Key and Wallet
2) Encrypt Data with ENCKEYS

35. 在 Oracle database 11.2.0.4中如何启用OGG复制?

The database services required to support Oracle GoldenGate capture and apply must be enabled explicitly for an Oracle 11.2.0.4 database. This is required for all modes of Extract and Replicat.

To enable Oracle GoldenGate, set the following database initialization parameter. All instances in Oracle RAC must have the same setting.

ENABLE_GOLDENGATE_REPLICATION=true

36. 协作模式下，投递进程是怎样工作的?

In a Coordinated Mode Replicat operates as follows:

Reads the Oracle GoldenGate trail.
Performs data filtering, mapping, and conversion.
Constructs SQL statements that represent source database DML or DDL transactions (in committed order).
Applies the SQL to the target through the SQL interface that is supported for the given target database, such as ODBC or the native database interface.

37. 经典投递和协作投递（Coordinated Replicat）的主要区别是什么?

The difference between classic mode and coordinated mode is that Replicat is multi-threaded in coordinated mode. Within a single Replicat instance, multiple threads read the trail independently and apply transactions in parallel. Each thread handles all of the filtering, mapping, conversion, SQL construction, and error handling for its assigned workload. A coordinator thread coordinates the transactions across threads to account for dependencies among the threads.

38. OGG 12c中如何创建一个协作投递(COORDINATED REPLICATE )进程?

You can create the COORDINATED REPLICATE with the following OGG Command:

ADD REPLICAT rfin, COORDINATED MAXTHREADS 50, EXTTRAIL dirdat/et

39. 在OGG 12c中创建一个投递进程，未指定 DISCARDFILE 参数，会怎样?

Starting with OGG 12c, if you don’t specify a DISCARDFILE OGG process now generates a dicard file with default values whenever a process is started with START command through GGSCI.

40. 是否可以让抽取进程在指定的CSN启动?

Yes, Starting with OGG 12c you can now start Extract at a specific CSN in the transaction log or trail.
Example:
START EXTRACT fin ATCSN 12345
START EXTRACT finance AFTERCSN 67890

41. 能否解释一下针对Oracle 12c投递时的并行机制?

Yes. The database parallel process are leveraged on the target database for automatic dependency aware parallel apply.

This key enhancement makes it very easy to maintain throughput and reducing latency. Previously the Replicat process had to manually be broken down into multiple threads.

42. OGG12c的集成交付中，读取队列文件的步骤有什么变化?

The trail generated by the extract process is read by Integrated Delivery and Logical Chase Records (LCR) are created. These LCR’S are then shipped over the network to the destination database.

43. 集成投递和协作投递（Coordinated delivery）的区别是什么?

Integrated delivery is the new 12c mechanism of sending extract trail to the destination in an Oracle enviornment. Coordinated delivery is the new mechanism to send data between now-Oracle databases.

=========================performance======================

44. 尝试列出一些可以提升 OGG投递性能的参数?

The parameters below can be used to improve the replicat performance:

BATCHSQL
GROUPTRANSOPS
INSERTAPPEND

45. Oracle Goldengate 复制时，需要监控哪些内容?

The lag and checkpoint latency of the Extract, pump and Replicat processes are normally monitored.

46. 什么情况下使用PASSTHRU模式?

In pass-through mode, the Extract process does not look up the table definitions, either from the database or from a data definitions file. This increases the throughput of the data pump, as the object definition look-up is bypassed.

47. 什么情况下，会造成抽取或传输进程变慢?

Some of the possible reasons are:

Long running batch transactions on a table.
Insufficient memory on the Extract side. Uncommitted, long running transactions can cause writing of a transaction to a temporary area (dirtmp) on disk. Once the transaction is committed it is read from the temporary location on the file system and converted to trail files.
Slow or overburdened Network.

48. 造成交付进程慢的主要原因有哪些?

Some of the possible reasons are:

Large amount of transactions on a particular table.
Blocking sessions on the destination database where non-Goldengate transactions are also taking place on the same table as the replicat processing.
If using DBFS, writing & reading of trail files may be slow if SGA parameters are not tuned.
For slow Replicat’s, latency may be due to missing indexes on target.
Replicat having to process Update, delete of rows in very large tables.

49. 抽取进程正常运行了很长时间，突然一下当掉了，一小时之后我重启了这个进程. 在这1小时内，数据库中提交的事务会怎样处理?

OGG checkpoint provides the fault tolerance and make sure that the transaction marked for committed is capture and captured only once. Even if the extract went down abnormally, when you start the process again it reads the checkpoint file to provide the read consistency and transaction recovery.

50. 使用集成抽取模式，并且使用了默认参数，当源端数据量增加时，抽取进程的延时超过1小时甚至更多，而且数据库的性能也在降低。如何解决这种性能问题?

When operating in integrated capture mode, you must make sure that you have assigned sufficient memory to STREAMS_POOL_SIZE. An undersized STREAMS_POOL_SIZE or limiting the streams pool to use a specific amount of memory can cause troubles.

The best practice is to allocate STREAMS_POOL_SIZE at the instance level and allocate the MAX. SGA at GG process level as below:
SQL> alter system set STREAMS_POOL_SIZE=3G

TRANLOGOPTIONS INTEGRATEDPARAMS (MAX_SGA_SIZE 2048, PARALLELISM 4)

51. 为什么需要在交付进程中对表进行拆分投递，应该如何做?

In OGG you can configure replicat at the data at the schema level or at the table level using TABLE parameter of extract and MAP parameter of replicat.

For replicating the entire database you can list all the schemas in the database in the extract/replicat parameter file.

Depending the amount of redo generation you can split the tables in a schema in multiple extracts and replicats to improve the performance of data replication. Alternatively youcan also group a set of tables in the confiuration by the application functionality.

Alternatively you may need to remove tables which have long running transactions in a seperate extract process to eliminte lag on the other tables.

Let’s say that you have a schema named SCOTT and it has 100 hundred tables.

Out of these hundred tables, 50 tables are heavily utilized by application.

To improve the overall replication performance you create 3 extract and 3 replicats as follows:

Ext_1/Rep_1 –> 25 tables
Ext_2/Rep_2 –> 25 tables
Ext_3/Rep_3 –> 50 tables
Ext_1/Rep_1 and Ext_2/Rep_2 contains 25 table each which are heavily utilized or generate more redo.
Ext_3/Rep_3 contains all the other 50 tables which are least used.

==================troubleshoot=================

52. 如果才能在日志文件中查看长事务?

The WARNLONGTRANS parameter can be specified with a threshold time that a transaction can be open before Extract writes a warning message to the ggs error log.

Example: WARNLONGTRANS 1h, CHECKINTERVAL 10m

53. 使用什么命令可以查看抽取进程的读取点信息?

Use the following command to view the Extract checkpoint information.
GGSCI> info extract , showch
GGSCI> info extract ext_fin, showch

54. RESTARTCOLLISION 参数与 HANDLECOLLISIONS 的区别是什么?

The RESTARTCOLLISION parameter is used to skip ONE transaction only in a situation when the GoldenGate process crashed and performed an operation (INSERT, UPDATE & DELETE) in the database but could not checkpoint the process information to the checkpoint file/table. On recovery it will skip the transaction and AUTOMATICALLY continue to the next operation in the trail file.

When using HANDLECOLLISION GoldenGate will continue to overwritten and process transactions until the parameter is removed from the parameter files and the processes restarted.

55. 如何查看抽取进程从日志中捕获的数据?

The logdump utility is used to open the trail files and look at the actual records that have been extracted from the redo or the archive log files.

56. 在配置了OGG的DB主机中，如果提示RMAN-08147 警告信息，是怎么回事?

This occurs when the V$ARCHIVED_LOG.NEXT_CHANGE# is greater than the SCN required by the GoldenGate Capture process and RMAN is trying to delete the archived logs. The RMAN-08147 error is raised when RMAN tries to delete these files.

When the database is open it uses the DBA_CAPTURE values to determine the log files required for mining. However if the database is in the mount state the V$ARCHIVED_LOG. NEXT_CHANGE# value is used.

See MetaLink note: 1581365.1

57. 如何使用logdump查看已经加密过的队列文件?

You must use the DECRYPT option before viewing data in the Trail data.

58. 列出一些Logdump中常用的命令，并且可以搜索队列文件中的数据.

Below are few logdump commands used on a daily basis for displaying or analyzing data stored in a trail file.

$ ./logdump – to connect to the logdump prompt
logdump> open /u01/app/oracle/dirdat/et000001 – to open a trail file in logdump
logdump> fileheader on – to view the trail file header
logdump> ghdr on – to view the record header with data
logdump> detail on – to view column information
logdump> detail data – to display HEX and ASCII data values to the column list
logdump> reclen 200 – to control how much record data is displayed
logdump> pos 0 – To go to the first record
logdump> next (or simply n) – to move from one record to another in sequence
logdump> count – counting records in a trail

=======================其它===================

59. 为什么有必要把OGG抽取进程升级成集成抽取模式?

Oracle is able to provide faster integration of the new database features by moving the GoldenGate Extraction processes into the database. Due to this, the GoldenGate Integrated Extract has a number of features like Compression which are not supported in the traditional Extract. You can read more about how to upgrade to Integrated Extract and more about Integrated Delivery. Going forward preference should be give to create new extracts as Integrated Extracts and also to upgrade existing traditional Extracts.

60. 集成投递的目标数据库最低版本要求是多少?

Oracle 11.2.0.4 is the the minimum required database version which supports both Integrated extract and Integrated Reaplicat.

61. GoldenGate 集成投递支持哪些数据库?

Oracle Integrated Delivery is only available for Oracle Databases.

62. 使用集成投递, 在哪里可以查看性能数据统计?

Yes with 12c, performance statistics are collected in the AWR repository and the data is available via the normal AWR reports.

63. 添加一张新的抽取取到OGG复制链路中的步骤是怎样的?

The steps to be executed would be the following:

Include the new table to the Extract & pump process.
Obtain starting database SCN and Copy the source table data to the target database
Start Replicat on target at the source SCN database point.

64. GoldenGate中的 CSN号，相当于Oracle 数据库中的什么对象?

It is equivalent of the Oracle database SCN transaction number.

65. 如何使用抽取进程生成一个CSV文件?

You will have to use the CSV Flat File Adaptor to create CSV files. The source would be the extract trail files which use the configuration of the adaptor settings to generate CSV files.

66. OGG安装目录下的DEFGEN程序是做什么用的?

When the source and the target schema objects are not the same (different DDL’s) the Replicat process needs to know the source definition of the objects. The output from the DEFGEN utility is used in conjunction with the trail data to determine which column value in the trail belongs to which column.

67. 我们的数据库中有压缩表，做OGG单向同步，需要注意哪些事项.

You must use OGG 11.2 and configure GoldenGate Integrated Capture process to extract data from compressed tables.

Note: Pre OGG 11.2 doesn’t support extracting data from compressed tables

68. 当前数据库是Oracle database 10.2.0.4,想使用集成抽取模式，应该如何做才能实现.

Oracle GoldenGate Integrated Capture process supports Oracle databases 10.2 and higher. But if you are running Oracle database 10.2 and want to you Oracle GoldenGate Integrated Capture process then you must configure downstream topology.

69. 现在我需要从一个非exadata平台迁移到exadata，源端使用的是OGG 11.1,目标端是OGG 11.2，这种环境中如何配置OGG进程?

It is recommended that all instances of Oracle GoldenGate be the same version to take advantage of the new functionality, but this is not possible all the time and is not required. In this scenario, OGG provides a parameter called ‘FORMAT RELEASE’ which allows customers to use different versions of Oracle GoldenGate Extract, trail files, and Replicat together.

Example: RmtTrail /u01/app/oracle/dirdat, Format Release 11.1

Note: The input and output trails of a data pump must have the same trail file version.

70. 使用OGG 初始化的方法有哪些?

OGG has 2 functionalities, one it is used for Online data Replication and second for Initial Loading.

If you are replicating data between 2 homogeneous databases then the best method is to use database specific method (Exp/Imp, RMAN, Transportable tablespaces, Physical Standby and so on). Database specific methods are usually faster than the other methods.

—If you are replicating data between 2 heterogeneous databases or your replicat involves complex transformations, then the database specific method can’t be used. In those cases you can always use Oracle GoldenGate to perform initial load.

Within Oracle GoldenGate you have 4 different ways to perform initial load.

Direct Load – Faster but doesn’t support LOB data types (12c include support for LOB)
Direct Bulk Load – Uses SQL*LOAD API for Oracle and SSIS for MS SQL SERVER
File to replicat – Fast but the rmtfile limit is 2GB. If the table can’t be fit in 1 rmtfile you can use maxfiles but the replicat need to be registered on the target OGG home to read the rmtfiles from source.
File to Database utility – depending on the target database, use SQL*LOAD for Oracle and SSIS for MS SQL SERVER and so on.

Oracle GoldenGate initial loading reads data directly from the source database tables without locking them. So you don’t need downtime but it will use database resources and can cause performance issues. Take extra precaution to perform the initial load during the non-peak time so that you don’t run into resource contention.

71. 在源和目标端都有一张表‘TEST’，但表结构不同，我该如何复制这张表的数据?

OGG by default assumes that the sources and target tables are identical. A table is said to be identical if and only if the table structure, data type and column order are the same on both the source and the target.

If the tables are not identical you must use the parameter ‘SOURCEDEFS’ pointing to the source table definition and ‘COLMAP’ parameter to map the columns from source to target.

72. OGG中删除队列文件的最佳方式是怎样的?

Use the manager process to delete the extract files after they are consumed by the extract/replicat process

PURGEOLDEXTRACTS /u01/app/oracle/dirdat/et*, USECHECKPOINTS, MINKEEPHOURS 2

73. 有什么参数可以使OGG只解析归档数据，而不是在线日志?

Use the TRANLOGOPTIONS ARCHIVEDLOGONLY option in the parameter file.

74. 现在有一条单向复制链路，运维人员想针对源和目标端服务器安装操作系统补丁，请说明一下在打补丁前后应该执行的操作步骤.

Procedure:

Check to make sure that the Extract has processed all the records in the data source (Online Redo/archive logs)
GGSCI> send extract , logend
(The above command should print YES)

Verify the extract, pump and replicat has zero lag.
GGSCI> send extract , getlag
GGSCI> send extract , getlag
GGSCI> send replicat , getlag
(The above command should pring “At EOF, no more records to process.”)

Stop all application and database activity.
Make sure that the primary extract is reading the end of the redolog and that there is no LAG at all for the processes.
Now proceed with stopping the processes:

Source:

Stop the primary extract
Stop the pump extract
Stop the manager process
Make sure all the processes are down.

Target:

Stop replicat process
Stop mgr
Make sure that all the processes are down.
Proceed with the maintenance
After the maintenance, proceed with starting up the processes: