Dameng database_ Common initialization parameters

          The database ID will be involved when initializing the database instance 、 Properties such as ： End ⼝ Number 、 page ⼤⼩、 Character set 、 Initialization configuration of case sensitive parameters , among ⼀ The scope of these parameters is the entire database instance ⽣ Life cycle , After initialization, it cannot be modified . In the actual operation process, these parameters are different , May affect data storage 、 Inquire about 、 Grouping has different effects .

         stay Linux In the environment , You can use... On the command line dminit help Command to view the initialized parameters .

 keyword                       explain （ The default value is ）
--------------------------------------------------------------------------------
INI_FILE                    Initialization file dm.ini Storage path 
PATH                        The path where the initial database is stored 
CTL_PATH                    Control file path 
LOG_PATH                    Log file path 
EXTENT_SIZE                 The cluster size used by the data file (16), Optional value ：16, 32, 64, Company ： page 
PAGE_SIZE                   Data page size (8), Optional value ：4, 8, 16, 32, Company ：K
LOG_SIZE                    Log file size (256), Unit is ：M, The scope is ：256M ~ 2G
CASE_SENSITIVE              Size sensitive (Y), Optional value ：Y/N,1/0
CHARSET/UNICODE_FLAG        Character set (0), Optional value ：0[GB18030],1[UTF-8],2[EUC-KR]
SEC_PRIV_MODE               Authority management mode (0), Optional value ：0[TRADITION],1[BMJ],2[EVAL]
LENGTH_IN_CHAR             VARCHAR Whether the type length is in characters (N), Optional value ：Y/N,1/0
SYSDBA_PWD                  Set up SYSDBA password (SYSDBA)
SYSAUDITOR_PWD              Set up SYSAUDITOR password (SYSAUDITOR)
DB_NAME                     Database name (DAMENG)
INSTANCE_NAME               Instance name (DMSERVER)
PORT_NUM                    Monitor port number (5236)
BUFFER                      System cache size (100), Company M
TIME_ZONE                   Set time zone (+08:00)
PAGE_CHECK                  Page check mode (0), Optional value ：0/1/2
PAGE_HASH_NAME              Set page check HASH Algorithm 
EXTERNAL_CIPHER_NAME        Set the default encryption algorithm 
EXTERNAL_HASH_NAME          set default HASH Algorithm 
EXTERNAL_CRYPTO_NAME        Set up the root key encryption engine 
RLOG_ENC_FLAG               Set whether the log file is encrypted (N), Optional value ：Y/N,1/0
USBKEY_PIN                  Set up USBKEY PIN
PAGE_ENC_SLICE_SIZE         Set page encryption fragment size , Optional value ：0、512、4096, Company ：Byte
ENCRYPT_NAME                Set the whole database encryption algorithm 
BLANK_PAD_MODE              Set space fill mode (0), Optional value ：0/1
SYSTEM_MIRROR_PATH         SYSTEM Data file image path 
MAIN_MIRROR_PATH           MAIN Data file mirroring 
ROLL_MIRROR_PATH            Rollback file image path 
MAL_FLAG                    Set on initialization dm.ini Medium MAL_INI(0)
ARCH_FLAG                   Set on initialization dm.ini Medium ARCH_INI(0)
MPP_FLAG                   Mpp Set when the library in the system is initialized dm.ini Medium mpp_ini(0)
CONTROL                     Initialize configuration file （ See the system administrator's Manual for the configuration file format ）
AUTO_OVERWRITE              Whether to cover all files with the same name (0) 0: No coverage  1: Partial coverage  2: Full coverage 
USE_NEW_HASH                Whether to use improved character types HASH Algorithm (1)
ELOG_PATH                   Specify the path of the log file generated during initialization 
AP_PORT_NUM                 Monitoring port for cooperative work in distributed environment 
DFS_FLAG                    Set on initialization dm.ini Medium DFS_INI(0)
DFS_PATH                    Enable dfs Specifies the default path of the data file when the 
DFS_HOST                    Specify the connection to the distributed system DFS Service address of (localhost)
DFS_PORT                    Specify the connection to the distributed system DFS Service port number of (3332)
DFS_COPY_NUM                Specifies the number of copies of the distributed system (3)
DFS_DB_NAME                 Specify the database name of the distributed system ( Default and DB_NAME Agreement )
SHARE_FLAG                  Specify the shared properties of the database in the distributed system (0)
REGION_MODE                 Specifies the block policy of the system table space data file of the database in the distributed system (0) 0: Micro strategy  1: Macro strategy 
HUGE_WITH_DELTA             Whether it only supports the creation of transactional HUGE surface (1) 1: yes  0: no 
RLOG_GEN_FOR_HUGE           Whether to generate HUGE surface REDO journal (0) 1: yes  0: no 
PSEG_MGR_FLAG               Whether to use management segment only to record transaction information (0) 1: yes  0: no 
CHAR_FIX_STORAGE           CHAR Whether to store by fixed length (N), Optional value ：Y/N,1/0
SQL_LOG_FORBID              Is it forbidden to open SQL journal (N), Optional value ：Y/N,1/0
DPC_MODE                    Appoint DPC Instance roles in the cluster (0) 0: nothing  1:MP 2:BP 3:SP, Value 1/2/3 You can also use MP/BP/SP Instead of 
HELP                        Print help 

        This article mainly introduces some commonly used initialization parameters .

1、 Page size （PAGE_SIZE）

The page size used by the data file . Value ：4、8、16、32, Company K. The default value is 8. Is an optional parameter .
The larger the page size you choose , be DM The larger the tuple length supported , But at the same time, space utilization may decline .
This parameter mainly affects the actual string length that can be stored in the database and the total length of a row of data .
This limit length is only applicable to the case of table creation , When defining variables and evaluating expressions , Can not be limited by the length of this limit .

2、 Cluster size （EXTENT_SIZE）

The cluster size used by the data file , That is, the number of consecutive pages each time a new segment space is allocated . Value 16、32、64. Company ： the number of pages . The default value 16. Is an optional parameter .

3、 Case sensitive （CASE_SENSITIVE）

Identifier case sensitive . When case sensitive , Lowercase identifiers should use " " Include , Otherwise, it will be automatically converted to uppercase by the system ; When case is insensitive , The system does not convert the case of identifiers , It is also not case sensitive when comparing identifiers . Parameter values Y、y、1 Express sensitivity ;N、n、0 Indicates insensitivity . The default value is Y. Is an optional parameter .
meanwhile ,CASE_SENSITIVE by N、n、0 and CHARSET/UNICODE_FLAG by 0 Not at the same time .

4、 Character set encoding （CHARSET/UNICODE_FLAG）

Character set options . Value 0 representative GB18030,1 representative UTF-8,2 Stands for Korean character set EUC-KR. The default is 0. Is an optional parameter .

5、VARCHAR Whether the type length is in characters （LENGTH_IN_CHAR）

VARCHAR Whether the length of the type object is in characters . Value 1、Y Said is ,0、N Indicate no . The default value is 0. Is an optional parameter .

1 or Y： It's all VARCHAR The length of a type object is in characters . In this case , The definition length is not really adjusted according to the character length , Instead, the stored length value is enlarged according to the theoretical character length . Therefore, the actual number of characters that can be inserted exceeds the defined length , This is also allowed . At the same time, it should be noted that , Length of bytes stored 8188 The upper limit remains unchanged , in other words , Even if the column length is defined as 8188 character , The total byte length of the string that can actually be inserted still cannot exceed 8188.

0 or N： no , all VARCHAR The length of the type object is in bytes .

give an example ： When length_in_char=0 when ,varchar The storage unit of type column is bytes , Such as ：varchar(10) Maximum storage 10 Bytes .
When length_in_char=1 when ,varchar The storage unit of type column is character （ namely 2 Bytes ）, Such as ：varchar(10) Maximum storage 20 Bytes .
 

6、 Space filling mode （BLANK_PAD_MODE）

When setting string comparison , Whether the end space filling mode is compatible ORACLE. Value 1 For compatibility ,0 Is incompatible . The default is 0. Is an optional parameter .

Simply speaking , Is comparing characters 、count Fields and other operations , Do you think ‘ a’ And ‘ a ’ equivalent . When BLANK_PAD_MODE=0 when , except group by Grouping and other strict operations , Compare characters 、 Statistical results , Think ‘ a’ And ‘ a ’ equivalent . When BLANK_PAD_MODE=1 when , Strictly distinguish between ‘ a’ And ‘ a ’.

In addition to the above parameters, which will affect the specific use , Many other parameters will also affect , It does not affect the modification during the use of the instance , But most parameters such as ： Default encryption algorithm 、 Default HASH Algorithm 、 Full database encryption algorithm, etc , Generally, it is only required to maintain consistency during backup and restore .


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