ALTER SESSION

This parameter defines the default state of constraints ('ENABLE' or 'DISABLE') in case the state wasn't explicitly specified during the creation (see also CREATE TABLE and ALTER TABLE (Constraints)).

Specifies the default consumer groups for users and roles. For more details about consumer groups, refer to Resource Manager topic.

This parameter can only be changed throughout the system using ALTER SYSTEM, but not for single sessions. However, the system-wide value is shown in the session parameter column.

Defines the escape character for the LIKE predicate (for more details, see Predicates) if it is not specified explicitly.

Defines the output format of data stored as HASHTYPE. The following values can be set:

• HEX: Simple ouput as hex string. For example: 550e8400e29b11d4a716446655440000
• UUID: UUID style output. For example: 550e8400-e29b-11d4-a716-446655440000
• BASE64: base64-encoded ascii string. For example: chatkYY/Tsai+DDVIukNnw
• BASE64URL: base64url-encoded ascii string. For example: chatkYY_Tsai-DDVIukNnw

The default value is HEX.

UUID only works for columns with data type HASHTYPE(16 byte). If the column size is set to a value other than 16 byte, 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.

The default value is 86400 (24 hours).

To disable the limit, set the attribute value to 0.

This parameter is used to reduce the priority of a session to conserve resources. The following values can be set:

• ON: The priority of the session is reduced. The resource manager then divides the weight of the user by the number of currently active sessions. The session will thus consume less resources, even across consumer groups.

• OFF: The priority of the session is not altered. This is the default value.

For more details about priorities, see Resource Manager.

Sets the date format used for conversions between dates and strings. For information on the possible formats, refer to the Date/Time Format Models section.

Sets the language of the date format used in abbreviated month and day formats and those written in full. Possible languages are English (ENG = Default) and German (DEU). The English language can be set using ENG or ENGLISH and the German language with DEU, DEUTSCH, and GERMAN.

For more information about date/time formats, refer to the Date/Time Format Models section.

Defines the first day of a week (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 details, 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 details, see Database Users and Roles, and Privileges.

This parameter can only be changed throughout the system using ALTER SYSTEM, but not for single sessions. However, the system-wide value is shown in the session parameter column.

Specifies the security rules for user passwords. For details for all the possible parameters, see Database Users and Roles, and Privileges.

This parameter can only be changed throughout the system using ALTER SYSTEM, but not for single sessions. However, the system-wide value is shown in the session parameter column.

Enables or disables profiling for new connections by setting the values ON or OFF. For more details, see Profiling.

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/lowercase, 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:

• 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.

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. For more details, see Adding New Packages to Existing Script Languages.

Sets the limit for TEMP DB RAM 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.

The parameter must be specified as an unsigned integer, optionally followed by a single-character unit symbol M (megabytes), G (gigabytes), or T (terabytes). There must be no space between the value and the unit symbol. For example: 10G is valid, but not 10GB or 10 G.

If a unit is not specified, the value is interpreted as megabytes.

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 the session's connection. The possible values are:

• 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.

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 TEMP DB RAM usage by all sessions. If the parameter is set to OFF, no limit is applied.

This parameter can only be changed system-wide using ALTER SYSTEM, not for single sessions. However, the system-wide value is shown in the session parameter column.

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 and 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 and time data types section.

Defines the behavior for +/- operators:

• 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, ...).

The result of subtracting two DATE values, which always results in an integer, is not changed.