223 OWA_CACHE

The OWA_CACHE package provides an interface that enables the PL/SQL Gateway cache to improve the performance of PL/SQL Web applications.

See Also:

For more information about implementation of this package:

• Oracle Fusion Middleware Administrator's Guide for Oracle HTTP Server

• Oracle Fusion Middleware User's Guide for mod_plsql

The chapter contains the following topics:

• Constants

• Summary of OWA_CACHE Subprograms

223.1 OWA_CACHE Constants

OWA_CACHE defines several constants to use when specifying parameter values.

• system_level CONSTANT VARCHAR(6) := 'SYSTEM';

• user_level CONSTANT VARCHAR(4) := 'USER';

223.2 Summary of OWA_CACHE Subprograms

This table lists the OWA_CACHE subprograms and briefly describes them.

Table 223-1 OWA_CACHE Package Subprograms

Subprogram	Description
DISABLE Procedure	Disables the cache for this particular request
GET_ETAG Function	Returns the tag associated with the cached content (used in the Validation technique model only)
GET_LEVEL Function	Returns the caching level (used in the Validation technique model only)
SET_CACHE Procedure	Sets up the cache headers for validation model cache type
SET_EXPIRES Procedure	Sets up the cache headers for expires model cache type
SET_NOT_MODIFIED Procedure	Sets up the headers for a not modified cache hit (used in the Validation technique model only)
SET_SURROGATE_CONTROL Procedure	Sets up the headers for a surrogate-control header for Web cache

223.2.1 DISABLE Procedure

This procedure disables the cache for this particular request.

Syntax

OWA_CACHE.DISABLE;

223.2.2 GET_ETAG Function

This function returns the tag associated with the cached content. It is used in the Validation technique only.

Syntax

OWA_CACHE.GET_ETAG
  RETURN VARCHAR2;

Return Values

The tag for cache hit, otherwise NULL.

223.2.3 GET_LEVEL Function

This returns the caching level. It is used in the Validation technique model only.

Syntax

OWA_CACHE.GET_LEVEL
  RETURN VARCHAR2;

Return Values

The caching level string ('USER' or 'SYSTEM') for cache hit, otherwise NULL.

223.2.4 SET_CACHE Procedure

This procedure sets up the cache headers for validation model cache type.

Syntax

OWA_CACHE.SET_CACHE(
   p_etag        IN       VARCHAR2,
   p_level       IN       VARCHAR2);

Parameters

Table 223-2 SET_CACHE Procedure Parameters

Parameter	Description
p_etag	The etag associated with this content
p_level	The caching level ('USER' or 'SYSTEM').

Exceptions

VALUE_ERROR is thrown if

• p_etag is greater than 55

• p_level is not 'USER' or 'SYSTEM'

223.2.5 SET_EXPIRES Procedure

This procedure sets up the cache headers for expires model cache type.

Syntax

OWA_CACHE.SET_EXPIRES(
   p_expires      IN       NUMBER,
   p_level        IN       VARCHAR2);

Parameters

Table 223-3 SET_EXPIRES Procedure Parameters

Parameter	Description
p_expires	The number of minutes this content is valid.
p_level	The caching level ('USER' or 'SYSTEM').

Exceptions

VALUE_ERROR is thrown if

• p_expires is negative or zero

• p_level is not 'USER' or 'SYSTEM'

• p_expires is > 525600 (1 year)

223.2.6 SET_NOT_MODIFIED Procedure

This procedure sets up the headers for a not-modified cache hit. It is used in the Validation technique only.

Syntax

OWA_CACHE.SET_NOT_MODIFIED;

Exceptions

VALUE_ERROR is thrown if If the etag was not passed in

223.2.7 SET_SURROGATE_CONTROL Procedure

This procedure sets the headers for a surrogate-control header for Web cache

Syntax

OWA_CACHE.SET_SURROGATE_CONTROL(
   p_value        IN       VARCHAR2);

Parameters

Table 223-4 SET_SURROGATE_CONTROL Procedure Parameters

Parameter	Description
p_value	The value to be passed as the Surrogate-Control header.

Exceptions

VALUE_ERROR is thrown if If p_value is greater than 55 in length.