Disable Caching for the System

7-18 System Administrators Guide for Oracle Business Intelligence Enterprise Edition

7.6.2.2 About Sharing the Presentation Services Query Cache

When users access Answers to run queries, Presentation Services caches the results of the queries. Presentation Services uses the request key and the logical SQL string to determine if subsequent queries can use cached results. If the cache can be shared, then subsequent queries are not stored. ■ SAGetSharedRequestKey: An ODBC procedure that takes a logical SQL statement from Presentation Services and returns a request key value. The following shows the syntax of this procedure: SAGetSharedRequestKeysql-string-literal The value of the request key is affected by the following factors: ■ Whether the Virtual Private Database option has been selected in the repository physical database object ■ Whether any session variables have been marked as Security Sensitive in the repository Presentation Services takes security sensitive variable values into consideration when computing the request key for logical requests against database objects marked as Virtual Private Databases. See Section 7.9, Managing the Oracle BI Presentation Services Cache Settings for more information about the Presentation Services query cache.

7.6.2.3 About Result Records

A result record is returned after you issue a purge cache command. The result record contains two columns. The first column is a result code and the second column is a short message that describes the result of the purge operation. Table 7–1 shows examples of result records.

7.6.2.4 Storing and Purging Cache for SAPBW Data Sources

In Microsoft Analysis Services, member caption name is the same as member unique name. However, in SAPBW data sources, member caption name is different from member unique name. Therefore, the Oracle BI Server maintains a cache subsystem for SAPBW member unique names. This subsystem is turned off by default. For configuration information, see the topic about the MDX Member Name Cache Section in Appendix A, NQSConfig.INI File Configuration Settings. When a query is received for member unique name, the subsystem checks the cache to determine whether cache exists for this query. If cache exists, then the record for the cached unique name is returned. If there is no cache that matches the query, then the subsystem sends a probing query to SAPBW. Table 7–1 Query Result Codes Result Code Result Message 1 SAPurgeCacheByDatabase returns successfully. 59115 Operation not performed because caching is not enabled. 59116 The database specified does not exist. 59117 The table specified does not exist. Managing Performance Tuning and Query Caching 7-19 The probing query is logged when the log level is equal or greater than 2. The status of the subsystem, such as if the subsystem is enabled and events such as start and shutdown events, are also written to the server log. Be aware of the following cache purge issues: ■ The size of multidimensional cache entries can grow very large. Therefore, a limit on the size of each member set has been established in the MDX_MEMBER_CACHE section of the NQSConfig.INI file. ■ The format of persisted cache might not be consistent after an upgrade. Therefore, you should purge all cache before a software upgrade. ■ The cache is populated the first time that the query runs. You should arrange to populate the cache during off-peak hours, to minimize performance impact. The following purge procedures are specific to SAPBW data sources: ■ SAPurgeALLMCNCache. Purges all SAPBW cache entries. The following shows the syntax of this procedure: SAPurgeALLIMCNCache ■ SAPurgeMCNCacheByCube. Purges all cache entries that are associated with the specified physical cube. The database name and cube name are the external names of the repository objects. The following shows the syntax of this procedure: SAPurgeMCNCacheByCube DBName, CubeName Table 7–2 describes the messages that are returned. Only users with administrative privileges can run ODBC purge procedures. Caution: With each increased logging level, performance is impacted. Use caution when increasing the log level for users. Note: In the Administration Tool, you can purge cache for an individual cube table by right-clicking the cube table, and then selecting Purge Member Cache. This must be performed in online mode by a user with administrator privileges. Table 7–2 SAP Purge Cache Return Codes and Messages Return Code Return Message 1 SAPurgeALLMCNCache returns successfully. 1 SAPurgeMCNCacheByCube returns successfully. 59116 The database specified does not exist. Note: If the database and physical cube are both wrong, then this result code is returned. 85025 The physical cube specified does not exist.