1. Cache Guide
  2. Defining Cache Groups
  3. Synchronous WriteThrough (SWT) Cache Group
  4. Restrictions with SWT Cache Groups

Restrictions with SWT Cache Groups

There are certain restrictions when using an SWT cache group.

The following restrictions apply when using an SWT cache group:

  • Only the ON DELETE CASCADE and UNIQUE HASH ON cache table attributes can be used in the cache table definitions.

    See ON DELETE CASCADE Cache Table Attribute for more information about the ON DELETE CASCADE cache table attribute.

    See Creating a Hash Index on the Primary Key Columns of the Cache Table for more information about the UNIQUE HASH ON cache table attribute.

  • A FLUSH CACHE GROUP statement cannot be issued on the cache group.

    See Flushing a User Managed Cache Group for more information about the FLUSH CACHE GROUP statement

  • The cache table definitions cannot contain a WHERE clause.

    See Using a WHERE Clause for more information about WHERE clauses in cache group definitions and operations.

  • A TRUNCATE TABLE statement cannot be issued on the cache tables.

  • SWT cache groups cannot cache Oracle Database views or materialized views.

  • You should avoid running DML statements directly on Oracle Database tables cached in an SWT cache group. This could result in an error condition. Any insert, update, or delete operation on the cached Oracle Database table can negatively affect the operations performed on TimesTen for the affected rows. TimesTen does not detect or resolve update conflicts that occur on the Oracle database. Committed changes made directly on a cached Oracle Database table may be overwritten by a committed update made on the TimesTen cache table when the cache table update is propagated to the Oracle database. In addition, deleting rows on the cached Oracle Database table could cause an empty update if TimesTen tries to update a row that no longer exists.

    To ensure that not all data is restricted from DML statements on Oracle Database, you can partition the data on Oracle Database to separate the data that is to be included in the SWT cache group from the data to be excluded from the SWT cache group.