Dameng V8 Requirements

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This document is intended to guide personnel who are implementing, maintaining, or integrating the Dameng database for the first time, step by step, to complete Dameng DM8 database initialization, MySQL compatibility mode configuration, service startup, and connection verification.

The examples in this document use the following plan:

Item	Example Value
Database Installation Directory	`/opt/dmdbms`
Database Storage Directory	`/dmdata/data`
DATABASE_NAME	`DMTEST`
Instance Name	`DBSERVER`
Database Port	`5236`
Administrator Account	`SYSDBA`
Administrator PASSWORD	`<SYSDBA_PASSWORD>`

Note: <SYSDBA_PASSWORD> and <SYSAUDITOR_PASSWORD> are placeholders in the document. In actual operations, please replace them with real passwords that meet complexity requirements. PASSWORD complexity requirements.

1. Pre-Operation Confirmation

1. Confirm Dameng is Installed

Execute on the server:

ls /opt/dmdbms/bin

If you can see files like dminit, dmserver, disql, this indicates that the Dameng software has been installed.

You can also check the version:

/opt/dmdbms/bin/dmserver

The following content may appear in the output:

dmserver V8
version: 03134284194-20240920-243574-20108

2. Confirm System User

Dameng usually runs the database using the dmdba user. Check if the user exists:

id dmdba

If it does not exist, it can be created by the user root:

groupadd dinstall
useradd -g dinstall -m -d /home/dmdba -s /bin/bash dmdba
passwd dmdba

3. Prepare the data directory

Use the following command to execute root user creation:

mkdir -p /dmdata/data
chown -R dmdba:dinstall /dmdata
chmod -R 775 /dmdata

The purpose of this step is to create a directory for storing database files and to grant permissions to the dmdba user.

2. Initialize the Database

Switch to the dmdba user to create:

su - dmdba

Execute the initialization command:

/opt/dmdbms/bin/dminit \
  PATH=/dmdata/data \
  PAGE_SIZE=32 \
  EXTENT_SIZE=32 \
  CASE_SENSITIVE=0 \
  UNICODE_FLAG=1 \
  DB_NAME=DMTEST \
  INSTANCE_NAME=DBSERVER \
  PORT_NUM=5236 \
  SYSDBA_PWD=<SYSDBA_PASSWORD> \
  SYSAUDITOR_PWD=<SYSAUDITOR_PASSWORD>

If the initialization is successful, you will see output similar to this:

create dm database success

After successful initialization, the database directory will be generated:

/dmdata/data/DMTEST

The key configuration file among them is:

/dmdata/data/DMTEST/dm.ini

3. Modify MySQL Compatibility Configuration

Edit the configuration file using the following method: root or dmdba created by the user:

vi /dmdata/data/DMTEST/dm.ini

Find and modify the following two configurations:

COMPATIBLE_MODE = 4
ORDER_BY_NULLS_FLAG = 0

If these two configurations already exist in the file, you can directly modify the existing lines.

Do not add configurations with the same names at the end of the file, otherwise duplicate configurations may occur, causing the actual effective values to differ from the expected ones.

After completing the modifications, you can use the following command to check:

grep -Ein 'COMPATIBLE_MODE|ORDER_BY_NULLS_FLAG' /dmdata/data/DMTEST/dm.ini

Expected to see:

COMPATIBLE_MODE = 4
ORDER_BY_NULLS_FLAG = 0

4. Register Database Service

Switch back to the root user to create:

exit

/opt/dmdbms/script/root/dm_service_installer.sh \
  -t dmserver \
  -p DBSERVER \
  -dm_ini /dmdata/data/DMTEST/dm.ini

After successful registration, the service name is usually:

DmServiceDBSERVER.service

Set up startup on boot and start the service:

systemctl daemon-reload
systemctl enable DmServiceDBSERVER.service
systemctl start DmServiceDBSERVER.service

Check service status:

systemctl status DmServiceDBSERVER.service --no-pager

If you see:

Active: active (running)

Indicates that the database service has started.

5. Verify if the database is available

1. Check the port

Execute:

ss -lntp | grep ':5236'

If you see dmserver listening on 5236, it indicates that the database port is normal.

Switch to the dmdba user to create:

su - dmdba

/opt/dmdbms/bin/disql SYSDBA/<SYSDBA_PASSWORD>@127.0.0.1:5236

Execute after successful login:

select 1 as OK;

If return:

OK
-----------
1

Indicates that the database connection is normal.

3. Verify if it is in MySQL compatibility mode

In disql:

select para_name, para_value
from v$dm_ini
where para_name in (
  'COMPATIBLE_MODE',
  'ORDER_BY_NULLS_FLAG',
  'INSTANCE_NAME',
  'PORT_NUM'
);

Execution, Expected Result:

INSTANCE_NAME        DBSERVER
PORT_NUM             5236
COMPATIBLE_MODE      4
ORDER_BY_NULLS_FLAG  0

Among them:

COMPATIBLE_MODE = 4

Indicates that the current database operating status has enabled MySQL compatibility mode.

Appendix 1, Detailed Description of Configuration Items

1. `PATH`

Example:

PATH=/dmdata/data

Meaning:

PATH is the root directory of the database files. During the initialization process, Dameng will create the database directory under this directory.

If DB_NAME=DMTEST, the final directory is usually:

/dmdata/data/DMTEST

This directory will store data files, log files, control files, and the dm.ini configuration file.

Recommendations:

It is recommended to place it on a data disk with sufficient capacity and stable performance in a production environment.
It is not recommended to place it in a temporary directory, such as /tmp.
Do not move the directory casually after initialization.

2. `DB_NAME`

Example:

DB_NAME=DMTEST

Meaning:

DB_NAME is the name DATABASE_NAME. It will affect the database directory name, log file name, etc.

For example, when DB_NAME=DMTEST, it usually generates:

/dmdata/data/DMTEST
/dmdata/data/DMTEST/DMTEST01.log
/dmdata/data/DMTEST/DMTEST02.log

Suggestions:

Use a single, clear DATABASE_NAME throughout the project.
It is not recommended to change it after initialization.

3. `INSTANCE_NAME`

Example:

INSTANCE_NAME=DBSERVER

Meaning:

INSTANCE_NAME is the name of the database instance. It is usually used to generate the service name when registering the service.

For example:

INSTANCE_NAME=DBSERVER

The service name after registration is usually:

DmServiceDBSERVER.service

Suggestions:

For a single instance on a single machine, you can use DBSERVER.
When deploying multiple instances on one machine, each instance name must be different.

4. `PORT_NUM`

Example:

PORT_NUM=5236

Meaning:

PORT_NUM is the database listening port. The application needs to access this port when connecting to the database.

The port entered on the program page must match this port:

HOST:172.17.9.84
PORT:5236

Suggestions:

The default port of Dameng is usually 5236.
If multiple Dameng instances exist on the same machine, ports cannot be duplicated.
After changing the port, the database service needs to be restarted.

5. `PAGE_SIZE`

Example:

PAGE_SIZE=32

Meaning:

PAGE_SIZE is the database page size, in KB. The database organizes data in units of pages when reading and writing data.

PAGE_SIZE=32 indicates that each data page is 32KB.

Impact:

It affects data storage, indexing, and I/O behavior.
It is not recommended to modify it after initialization.
If adjustment is needed, it usually requires reinitializing the database and migrating data.

Recommendation:

If there is an SOP for this scenario, follow the SOP.
Do not change it casually unless there are special requirements.

6. `EXTENT_SIZE`

Example:

EXTENT_SIZE=32

Meaning:

EXTENT_SIZE is the cluster size, measured in pages. It can be understood as the basic unit of space allocation used by the database at a time.

If:

PAGE_SIZE=32
EXTENT_SIZE=32

So a cluster is approximately:

32KB * 32 = 1024KB

About 1MB.

Impact:

Will affect the granularity of data file space allocation.
Not recommended to modify after initialization.

7. `CASE_SENSITIVE`

Example:

CASE_SENSITIVE=0

Meaning:

CASE_SENSITIVE indicates whether database object names are case-sensitive.

Common values:

0:CASE_INSENSITIVE
1:CASE_SENSITIVE

For example, when case is not distinguished, the following two table names can be considered as the same object:

user
USER

Impact:

Will affect the identification of table names, column names, and object names.
For MySQL migration or MySQL-compatible scenarios, it is generally preferred to configure as 0.
It is not recommended to modify after initialization.

8. `UNICODE_FLAG`

Example:

UNICODE_FLAG=1

Meaning:

UNICODE_FLAG is a character set configuration.

Common values:

0:GB18030
1:UTF-8
2:EUC-KR

UNICODE_FLAG=1 indicates that the database uses the UTF-8 character set.

Recommendations:

It is recommended to use UTF-8 for new systems.
Better compatibility with Chinese, English, and multilingual characters.
It is not recommended to modify after initialization.

9. `SYSDBA_PWD`

Example:

SYSDBA_PWD=<SYSDBA_PASSWORD>

Meaning:

SYSDBA_PWD is the administrator account with PASSWORD SYSDBA.

SYSDBA is similar to a database super administrator, with advanced permissions.

Suggestions:

Use a strong PASSWORD.
Do not use simple passwords such as SYSDBA, 123456, password.
PASSWORDs are recommended to be at least 8 characters long and include letters and numbers.
Do not write actual PASSWORDs in external documents.

10. `SYSAUDITOR_PWD`

Example:

SYSAUDITOR_PWD=<SYSAUDITOR_PASSWORD>

Meaning:

SYSAUDITOR_PWD is the audit administrator account of PASSWORD SYSAUDITOR.

SYSAUDITOR is mainly used for management functions related to auditing.

Recommendations:

Use a PASSWORD different from SYSDBA.
Use a strong PASSWORD that meets complexity requirements.

11. `COMPATIBLE_MODE`

Example:

COMPATIBLE_MODE = 4

Meaning:

COMPATIBLE_MODE is the compatibility mode configuration of the Dameng database, used to control which type of database the database conforms to in terms of syntax, functions, and certain behaviors. SQL syntax, functions, and certain behaviors.

Common value meanings:

0:DEFAULT_MODE
1:SQL92
2:Oracle
3:MS SQL Server
4:MySQL
5:DM6
6:Teradata
7:PostgreSQL
8:DB2

This text is configured as:

COMPATIBLE_MODE = 4

Indicates enabling MySQL compatibility mode.

Function:

Improves the compatibility of MySQL SQL syntax with Dameng.
Reduces migration or adaptation efforts from MySQL to Dameng.

Note:

This configuration does not mean Dameng supports the MySQL protocol.
Programs still need to internally use the Dameng driver; if there is no driver configuration option on the page, users do not need to fill it in separately.
A database service restart is required after modification.
Whether it ultimately takes effect should be determined by the v$dm_ini query results.

12. `ORDER_BY_NULLS_FLAG`

Example:

ORDER_BY_NULLS_FLAG = 0

Meaning:

ORDER_BY_NULLS_FLAG is used to control whether NULL values appear at the beginning or the end when sorting with NULL. ORDER BY.

Reason:

Different databases may have different default behaviors for sorting NULLs. When migrating an application from MySQL to Dameng, if the sort results depend on the position of NULLs, this parameter may affect the order of query results.

This article is configured as:

ORDER_BY_NULLS_FLAG = 0

The purpose is to make the sorting behavior closer to MySQL usage habits.

Note:

After modification, the database service needs to be restarted.
If the business SQL has explicitly specified NULLS FIRST or NULLS LAST, the behavior specified in the SQL should take precedence.

Appendix 2, Common Issues

1. Why can’t I use the MySQL client even after setting MySQL compatible mode?

Because MySQL compatible mode only affects SQL syntax and certain database behaviors; it does not change Dameng’s network protocol.

When applications or tools connect to Dameng, they still need to use the Dameng driver:

dm.jdbc.driver.DmDriver
jdbc:dm://<host>:5236

Cannot use:

com.mysql.cj.jdbc.Driver
jdbc:mysql://<host>:5236

2. How to confirm that the configuration is indeed effective?

Do not just look at the dm.ini file; it is recommended to log in to the database to check the runtime status:

select para_name, para_value
from v$dm_ini
where para_name in ('COMPATIBLE_MODE', 'ORDER_BY_NULLS_FLAG');

The running status is considered effective only when the following results are seen:

COMPATIBLE_MODE      4
ORDER_BY_NULLS_FLAG  0

3. Why didn’t the changes take effect `dm.ini`?

Common reasons:

The database service was not restarted after the changes.
There are duplicate configuration items in the file.
The modified file is not the one currently being used by the dm.ini instance.

You can check which configuration file the current instance is using through the service start command:

systemctl status DmServiceDBSERVER.service --no-pager

You will usually see something like the following in the output:

dmserver path=/dmdata/data/DMTEST/dm.ini -noconsole

4. If I… what should I do if a complexity error occurs during PASSWORD initialization?

This indicates that the PASSWORD is too simple. Please switch to a more complex PASSWORD distribution package, for example:

AT_LEAST 8 POSITION
CONTAINS_LETTERS_AND_NUMBERS
AVOID_USING_THE_ACCOUNT_NAME_ITSELF

5. Can these parameters be changed later?

No.

Initialization parameters are generally not recommended to be changed later, such as:

‘PAGE_SIZE’
‘EXTENT_SIZE’
‘CASE_SENSITIVE’
‘UNICODE_FLAG’
‘DB_NAME’
‘INSTANCE_NAME’

If these parameters are configured incorrectly, it is usually recommended to reinitialize the database and migrate the data again.

‘dm.ini’ parameters can be adjusted later, such as:

‘COMPATIBLE_MODE’
‘ORDER_BY_NULLS_FLAG’
‘PORT_NUM’

However, after modification, it usually requires restarting the database service.

Appendix 3: Final Checklist

The ‘/dmdata/data’ data directory has been created.
The data catalog host is ‘dmdba:dinstall’.
The database has been successfully initialized.
‘/dmdata/data/DMTEST/dm.ini’ exists.
COMPATIBLE_MODE = 4.
ORDER_BY_NULLS_FLAG = 0.
The database service DmServiceDBSERVER.service is active.
Port 5236 is being listened to.
SYSDBA can log in to the database.
In v$dm_ini, the runtime value COMPATIBLE_MODE is 4.

1. Pre-Operation Confirmation

1. Confirm Dameng is Installed

2. Confirm System User

3. Prepare the data directory

2. Initialize the Database

3. Modify MySQL Compatibility Configuration

4. Register Database Service

5. Verify if the database is available

1. Check the port

2. Local Login Test

3. Verify if it is in MySQL compatibility mode

Appendix 1, Detailed Description of Configuration Items

1. PATH

2. DB_NAME

3. INSTANCE_NAME

4. PORT_NUM

5. PAGE_SIZE

6. EXTENT_SIZE

7. CASE_SENSITIVE

8. UNICODE_FLAG

9. SYSDBA_PWD

10. SYSAUDITOR_PWD

11. COMPATIBLE_MODE

12. ORDER_BY_NULLS_FLAG

Appendix 2, Common Issues

1. Why can’t I use the MySQL client even after setting MySQL compatible mode?

2. How to confirm that the configuration is indeed effective?

3. Why didn’t the changes take effect dm.ini?

4. If I… what should I do if a complexity error occurs during PASSWORD initialization?

5. Can these parameters be changed later?

Appendix 3: Final Checklist

1. `PATH`

2. `DB_NAME`

3. `INSTANCE_NAME`

4. `PORT_NUM`

5. `PAGE_SIZE`

6. `EXTENT_SIZE`

7. `CASE_SENSITIVE`

8. `UNICODE_FLAG`

9. `SYSDBA_PWD`

10. `SYSAUDITOR_PWD`

11. `COMPATIBLE_MODE`

12. `ORDER_BY_NULLS_FLAG`

3. Why didn’t the changes take effect `dm.ini`?