Data store attributes

Data store attributes are set at data store creation time.The data store attributes are listed inTable 1-1, "Data store attributes" and described in detail in this section.

These attributes can be assigned values only during data store creation by the instance administrator.

Data Source Name

The data source name uniquely identifies the attributes to a connection. It serves two purposes:

• As a unique identifier to the ODBC driver manager (if one is present), allowing it to associate a Data Store Name with a specific ODBC driver.

• As one of potentially many name aliases to a single physical data store where the name alias has unique attributes associated with it.

The data store attributes can apply to either the data source name (connection to a data store) or the Data Store Path Name (data store).

On Windows, the data source name and all configuration information associated with the data source (including the data store path name) are stored in the system registry. This information is used by the ODBC driver manager and by TimesTen.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set Data Source Name as follows:

DataStore

The data store path name uniquely identifies the physical data store. It is the full path name of the data store and the file name prefix, for example: C:\data\AdminData. This name is not a file name. The actual data store file names have suffixes, such as .ds0 and .log0, for example C:\data\AdminData.ds0 and C:\data\AdminData.log0.

You can use environment variables in the specification of the data store path and name.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set DataStore as follows:

DatabaseCharacterSet

The database character set determines the character set in which data is stored.

Generally, your database character set should be chosen based on the data requirements. For example: Do you have data in Unicode or is your data in Japanese on UNIX (EUC) or Windows (SJIS)?

You should choose a connection character set that matches your terminal settings or data source. See "ConnectionCharacterSet".

When the database and connection character sets differ, TimesTen performs the data conversion internally based on the connection character set. If the connection and database character sets are the same, TimesTen does not need to convert or interpret the data set. Best performance occurs when connection and database character sets match, since no conversion is required.

To use this attribute you must specify a supported character set. For a list of character set names that can be used as a value for this attribute, see "Supported Character Sets" in Oracle TimesTen In-Memory Database Operations Guide.

There are several things to consider when choosing a character set for your data store. For a discussion about these considerations, see "Choosing a database character set" in Oracle TimesTen In-Memory Database Operations Guide.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set DatabaseCharacterSet name as follows:

See also

"ConnectionCharacterSet"

Description

Optionally, set this attribute to help you identify the Data Source Name (DSN) and its attributes.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set Description as follows:

LogDir

The LogDir attribute specifies the directory where data store logs reside. Specifying this attribute allows you to place the transaction log files on a different I/O path from the data store checkpoint files. This may improve throughput.

You can use environment variables in the specification of the transaction log file path name. For example, you can specify $HOME/AdminDS for the location of the data store. See "Using environment variables in data store path names" in Oracle TimesTen In-Memory Database Operations Guide for more information.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set LogDir as follows:

Preallocate

The Preallocate attribute determines whether TimesTen preallocates file system space for the data store when the data store is created. Setting this attribute ensures that there will be sufficient space for the data store when the data store is saved to the file system.

Using Preallocate=1 in combination with ttRestore or ttRepAdmin -duplicate and a value of PermSize that does not match the value of PermSize of the original data store may result in two checkpoint files with different sizes. This has not been shown to have negative effects. However, the issue can be avoided completely either by using the same PermSize as the original data store or by setting Preallocate=0.

When a duplicate operation is carried out, the duplicated store has behavior consistent with a Preallocate setting of 0, even if it is set to 1 on the original or duplicated data store. The behavior is indicated by the size of the checkpoint files, which is the sum of the size of the data and size of the database header.

The checkpoint files are subsequently allowed to grow to the same size as checkpoint files on the master data store (PermSize + database header), but the space is not preallocated. The checkpoint files increase in size as data is added.

The reason for this behavior is that PreAllocate is set at database creation time. It is not a first connection attribute. The duplicate operation is not a database creation operation, so the preallocate attribute is not honored.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set Preallocate as follows:

Temporary

Set this attribute to create a temporary data store. Temporary data stores are not saved to the file system. They may, however, be shared and therefore require a data store path name. A temporary data store is deleted when the last connection is closed. See "Data store persistence" in Oracle TimesTen In-Memory Database Operations Guide for more information. You cannot assign the Temporary data store attribute to an existing permanent data store.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set Temporary as follows:

TypeMode

Specifies whether the names and semantics of the data types follow Oracle or TimesTen type rules. TimesTen supports both Oracle and TimesTen data types. The type mode determines what names are used to specify each data type. In some cases, a data type has both an alias name and a fixed type name. In such a situation, you can use either name. The TimesTen type mode is included for backward compatibility. We recommend that you use the default setting, which is Oracle type mode.

When caching Oracle data in TimesTen, TypeMode must be set to 0.

See "Type specifications" in Oracle TimesTen In-Memory Database SQL Reference for a list of data types and their fixed and alias names.

Required privilege

Only the instance administrator can change the value of this attribute.

Setting

Set TypeMode as follows: