Use this statement to configure System-wide parameters.
You need the ALTER SYSTEM system privilege.
- The session-based parameters are initialized with the system-wide parameters ALTER SYSTEM. However, you can overwrite it with the ALTER SESSION statement. The current settings are available in the EXA_PARAMETERS system table.
- If a value is changed through ALTER SYSTEM, it will only impact new connections to the database.
- The following table describes the parameters you can set:
HEX: Simple ouput as hex string (e.g. 550e8400e29b11d4a716446655440000)
UUID: UUID style output (e.g. 550e8400-e29b-11d4-a716-446655440000)
- ON: The query cache is used. Each query result that is expensive enough (defined internally by resource usage) is read from and written into the cache.
- OFF: The query cache is not used.
- READONLY: Results are read from the cache, however, additional new queries will not be cached.
- OFF: Snapshot mode is off and queries selecting from system tables or user tables will take read locks on those tables.
- SYSTEM TABLE: Snapshot mode is on and queries selecting from system tables will not take read locks on them. However, queries selecting from user tables will continue to get read locks on them.
- INTERVAL: The difference of two datetime values is an interval. When adding a decimal value to a timestamp, the number is rounded to an integer and a full day is added.
- DOUBLE: The difference of two datetime values is a double. When adding a decimal value to a timestamp, the fraction of days is added (hours, minutes, ...).
This parameter defines the default state (
Specifies the default consumer groups for users and roles. For more details about consumer groups, see Resource Manager.
Defines the escape character for the LIKE predicate (for more details, see Predicates) if it is not specified explicitly.
The parameter HASHTYPE_FORMAT defines the output format of data that is stored as HASHTYPE. The following values can be set:
The default value is
UUID only works for HASHTYPE columns of size 16 BYTE. If your column has a different size the output will be in HEX even if you set it to UUID.
Specifies a timeout in seconds. The session is killed after the specified time if there is no activity. To disable the limit, set the attribute to
The default value is 86400 seconds (24 hours).
Sets the date format used for conversions between dates and strings.
For information about date/time formats, see Date/Time Format Models.
Sets the language to use when full or abbreviated format for day and month. Possible languages are English (default) and German. English can be set using ENG or ENGLISH and German with DEU, DEUTSCH, or GERMAN.
For information about date/time formats, see Date/Time Format Models.
Defines the first day of a week as an integer 1-7 for Monday – Sunday.
Defines the decimal and group characters used for representing numbers. This parameter is also relevant to the use of numeric format models.
For more information, see Numeric Format Models.
Sets the timestamp format used for conversions between timestamps and strings. For information on the possible formats, refer to the Date/Time Format Models section.
Specifies the expiry rules for user passwords. These system values can be overwritten for single users through ALTER USER statement.
For more information, see Database Users and Roles and Privileges.
Specifies the security rules for user passwords. For details for all the possible parameters, see Database Users and Roles and Privileges.
Enables or disables profiling for new connections by setting the values
Existing connections are not affected, only connections that are created after the ALTER command.
The parameter QUERY_CACHE defines the usage of a read cache for SELECT queries. If the syntactically identical query is sent multiple times (except upper/lower case, spaces, ...), then the database can read the result directly out of a cache instead of executing the query. This is only applicable if the corresponding schema objects haven't changed in the meantime.
The following values can be set:
Whether a query was returned from the cache can be determined by the column EXECUTION_MODE in the corresponding system tables (EXA_SQL_LAST_DAY).
Defines how many seconds a statement may run before it is automatically aborted. When this point is reached, the statement may finish with an exception within a few seconds through an internal cancellation point. If this fails (for example because there are no such cancellation points or the query is slowed down due to disk operations) the query is terminated forcefully and the transaction is rolled back (including an internal reconnect).
Time spent waiting for other transactions (in state Waiting for session) is included. In case of EXECUTE SCRIPT the QUERY_TIMEOUT is applied to the script as a whole, and when reaching the timeout the script is terminated (including any statements being executed by the script).
Any changes of the QUERY_TIMEOUT within a script will only be applied when the script exits. The default value for QUERY_TIMEOUT is '0' (no restrictions).
Defines the script language aliases.
|Defines the hostname (or IP address) and the port number of a server to which the standard output (for example, by Python's print function) of UDF scripts are forwarded. You can deactivate the redirection of the script output by setting this parameter to the empty string.
Sets the limit for tempDBRAM usage by each session. If the parameter is set to OFF, no limit is applied. Users can alter this parameter for an individual session. The strictest limit will apply.
Since TEMP_DB_RAM can be swapped to disk, SESSION_TEMP_DB_RAM_LIMIT can be set to a larger value than the DB_RAM size.
Defines the transaction Snapshot Mode for connections. The possible values are:
For more information, see Snapshot Mode.
Defines a preprocessor script. If the script is specified (a regular script which was created through CREATE SCRIPT), then every executed SQL statement is preprocessed by that script. For more information on SQL preprocessing, see SQL Preprocessor. For details about the script language, see Scripting.
Appropriate user privileges must exist for executing this script. You can deactivate the preprocessing by specifying the empty string '' or NULL.
Defines the maximum significant digits used when casting from geometry data type to a string. You can use it to convert from geometry data type to string. It does not have any influence on the internal storage of geometry type, and on the geometry operations. The default value is 16, and the allowed range is <1,16>. For additional information, refer to the Type Conversion Rules section.
Sets the limit for total tempDBRAM usage by all sessions. If the parameter is set to OFF, no limit is applied.
Since TEMP_DB_RAM can be swapped to disk, TEMP_DB_RAM_LIMIT can be set to a larger value than the DB_RAM size.
Defines the time zone in which the values of type TIMESTAMP WITH LOCAL TIME ZONE are interpreted. For more information, refer to the Date/Time Data Types section. The list of supported timezones is available in the system table EXA_TIME_ZONES. The function SESSIONTIMEZONE returns the current session time zone.
Defines the course of action for ambiguous and invalid timestamps within a certain time zone. For more information, refer to the Date/Time Data Types section.
Defines the behavior for +/- operators:
Sets the limit for total tempDBRAM usage by all sessions of a user. If the parameter is set to OFF, no limit is applied.
Since TEMP_DB_RAM can be swapped to disk, USER_TEMP_DB_RAM_LIMIT can be set to a larger value than the DB_RAM size.