129
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.

The chapter contains the following topics:

• Using OWA_CACHE
• Summary of OWA_CACHE Subprograms

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Using OWA_CACHE

• Constants

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Constants

• system_level CONSTANT VARCHAR(6) := 'SYSTEM';
• user_level CONSTANT VARCHAR(4) := 'USER';

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Summary of OWA_CACHE Subprograms

Table 129-1  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

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DISABLE Procedure

This procedure disables the cache for this particular request.

Syntax

OWA_CACHE.DISABLE;

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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.

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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.

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SET_CACHE Procedure

This 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 129-2  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'

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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 129-3  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)

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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

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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 129-4  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.