Cache Fusion reads occur when a user on one Oracle system queries a block and then a user on another system queries the same block. The block is passed over the high speed interconnect (versus being read from disk). Cache fusion writes occur when a block previously changed by another instance needs to be written to disk in response to a checkpoint or cache aging.
As of July 2011, Oracle added an Exadata Storage Expansion Rack that allows you to grow storage capacity of the X2-2 and X2-8 by connecting to it via InfiniBand. This addition is great news for those who are looking to have Petabytes of information. It is also welcome news for those who would like to store more of their archived-to-tape data on disk.
The nice thing about Oracle hybrid columnar compression is that operations are faster because the query runs without decompression. The compressed version is processed in the Flash Cache, which results in lower I/O. The compressed version is also sent over InfiniBand; it is cloned compressed; and it is even backed up compressed! As a result, it scans much less (compressed) data!
Oracle has two very important parameters to use to test major features of Exadata: CELL_OFFLOAD_PROCESSING and _KCFIS_STORAGEIDX_DISABLED.
A helpful memory command that you can use to monitor the Oracle SGA is the ipcs command. The ipcs command displays the size of each shared memory segment for the SGA.
If mutex or latch waits are high but shared and Java pool freespace is also high, consider reducing the size of the shared and/or Java pools. When this happens, it could indicate that sessions are spending time scanning the unnecessarily large list of free shared pool chunks (be very careful before you do this—the goal is to get everything in memory—so ensure that you have enough allocated).
Part of the performance monitoring of the Integration Services service includes configuring the logging of performance counters. These counters enable you to view and understand the use of resources consumed during the execution of SSIS packages.
SQL Server Integration Services (SSIS) is a solution that provides enterprise-level data integration and workflow solutions that have as their goal the extraction, transformation, and loading (ETL) of data from various sources to various destinations. SSIS includes a wide range of tools and wizards to assist in the creation of the workflow and data flow activities that you need to manage in these complex data-movement solutions.
Bitmap indexes are most helpful in a data warehouse environment because they are generally great (fast) when you are only selecting data. A bitmap index is smaller than a b-tree index because it stores only the ROWID and a series of bits. In a bitmap index, if a bit is set, it means that a row in the corresponding ROWID (also stored) contains a key value
The bitmap join index in Oracle is a lot like building a single index across two tables. You must build a primary key or unique constraint on one of the tables. When you are looking for information from just the columns in the index or a count, then you will be able to access the single join index.