What is result cache in Oracle 11g?
Result Cache is a new feature in Oracle 11g and it does exactly what its name implies, it caches the results of queries and puts it into a slice of the shared pool. If you have a query that is executed often and reads data that rarely changes, this feature can increase performance significantly.
Does Oracle cache query results?
Oracle recommends client result caching for queries of read-only or read-mostly tables. Note: The client result cache is distinct from the server result cache, which resides in the SGA. When client result caching is enabled, the query result set can be cached on the client, server, or both.
What is PL SQL function result cache?
The cross-session PL/SQL function result cache provides a simple way to boost the performance of PL/SQL functions by saving the results of function calls for specific combinations of input parameters in the SGA. These results can be reused by any session calling the same function with the same parameters.
How do you use result cache?
When a query with RESULT_CACHE hint is run, Oracle will see if the results of the query have already been executed, computed, and cached, and, if so, retrieve the data from the cache instead of querying the data blocks and computing the results again.
What is a cached result?
The Use cached results option reuses results from a previous run of the same query unless the tables being queried have changed. Using cached results is only beneficial for repeated queries. For new queries, the Use cached results option has no effect, though it is enabled by default.
How do I clear my result cache?
BYPASS Procedure
- Place the result cache in bypass mode, and flush existing result. BEGIN DBMS_RESULT_CACHE.BYPASS(TRUE); DBMS_RESULT_CACHE.FLUSH; END; /
- Apply the PL/SQL code patches.
- Resume use of the result cache, by turning off the cache bypass mode. BEGIN DBMS_RESULT_CACHE.BYPASS(FALSE); END; /
What is cache in Oracle SQL?
Oracle Database Cache improves the scalability and performance of applications that access Oracle databases by caching frequently used data on a middle-tier system. With Oracle Database Cache, your applications can process several times as many requests as their original capacity.
How does database buffer cache work in Oracle?
The buffer cache is the in-memory area of the SGA where incoming Oracle data blocks are kept. On standard Unix databases, the data is read from disk into the Unix buffer where it is then transferred into the Oracle buffer. The size of the buffer cache can have a huge impact on Oracle system performance.
Why is cache faster than database?
In the case of the cache on a web site, it’s faster because the data has already been retrieved from the database (which, in some cases, could be located anywhere in the world). So it’s about locality, mostly. Cache eliminates the data transfer step.
What problems do cache solve?
Caches are useful when two or more components need to exchange data, and the components perform transfers at differing speeds. Caches solve the transfer problem by providing a buffer of intermediate speed between the components.
How do you check if a table is cached in Oracle?
- Setup. Set up the following schema objects to see how the SQL query cache works.
- Test It. Query the test table using the slow function and check out the elapsed time.
- RESULT_CACHE_MODE. The default action of the result cache is controlled by the RESULT_CACHE_MODE parameter.
- Scalar Subquery Caching.
Is there a result cache in Oracle 11g?
For example, Oracle Database’s Result Cache feature, which was introduced with Oracle Database 11 g Release 1, has received a lot of attention for its ability to cache SQL query and PL/SQL function results in memory.
How long does it take to cache a query in Oracle?
If the information is not present, it will cache the results of the query provided there is enough room in the result cache. Since we have no cached results, we would expect the first run to take approximately five seconds, but subsequent runs to be much quicker.
How is the result cache used in SQL?
Result Cache enables caching SQL query and PL/SQL function results to be stored in memory. Subsequent executions of the same query or function can be served directly out of the cache, improving response times. This technique can be especially effective for SQL queries and PL/SQL functions that are executed frequently.
What kind of cache does Oracle PL / SQL use?
Oracle saves query output with materialized views, global temporary tables, PL/SQL collections and with the new 11g result cache. A sharable PL/SQL collection – Oracle PL/SQL allows for result sets to be saved in RAM for later use by the session using an array heap called a “collection”.
