1. Cache Guide
  2. Methods for Transmitting Changes Between TimesTen and Oracle Databases
  3. Setting a Passthrough Level

Setting a Passthrough Level

When an application issues SQL statements on a TimesTen connection, the SQL statement can be performed in the TimesTen database or passed through to the Oracle database to be performed. Whether the SQL statement is performed in the TimesTen or Oracle database depends on the composition of the statement and the setting of the PassThrough connection attribute.

You can set the PassThrough connection attribute to define which statements are to be performed locally in TimesTen and which are to be redirected to the Oracle database for processing.

The passthrough level can be set at any time and takes effect immediately. The value can be set to 0 through 3. When appropriate within passthrough levels 1 through 3, TimesTen connects to the Oracle database using the current user's credentials. You can use either an Oracle Wallet set up with the cache administration user credentials pointed to by the PWDWallet connection attribute or provide the cache administration user name in the UID connection attribute and the OraclePwd connection attribute as the Oracle password. See Providing Both Cache Administration Users and Passwords in the Oracle TimesTen In-Memory Database Security Guide.

Passing through update operations to the Oracle database for processing is not recommended when issued on cache tables in an AWT or SWT cache group. See Considerations for Using Passthrough.

Note:

A transaction that contains operations that are replicated with RETURN TWOSAFE cannot have a PassThrough setting greater than 0. If PassThrough is greater than 0, an error is returned and the transaction must be rolled back.

When PassThrough is set to 0, 1, or 2, the following behavior occurs when a dynamic load condition exists:

  • A dynamic load can occur for a SELECT operation on cache tables in any dynamic cache group type.

  • A dynamic load for an INSERT, UPDATE, or DELETE operation can only occur on cached tables with dynamic AWT or SWT cache groups.

See Dynamic Cache Groups.

The following sections describe the different passthrough options: