The DBMS_JOB package is actually an API into an Oracle subsystem known as the job queue. The Oracle job queue allows for the scheduling and execution of PL/SQL routines (jobs) at predefined times and/...
Fragmentation in a tablespace is thought to be a performance killer. This has been proven to be a myth. Fragmentation by itself does not cause performance problems in a multi-user Oracle database. Wha...
The flash recovery area, which allows you to centralize storage of all recovery-related files, is new in Oracle 10g. The flash recovery area is an area of disk that is defined for use for recovery-rel...
Adding an ASM Disk Group ASM disk groups are the foundation of ASM. It is where your data will be stored. ASM disk groups can be allocated to raw disk, cooked disk. To add a ASM disk group you first...
The db file scattered read wait event is similar to the db file sequential read, except that the session is waiting for a multi-block I/O read request to complete. The db file scattered read waits are...
A direct path read I/O operation reads data into the session's PGA instead of the SGA. Direct read I/Os may be performed in synchronous or asynchronous mode, depending on the platform and the value of...
This wait event only occurs when Flashback Database is turned on. A session waits for recovery writer (RVWR) to write flashback data to the flashback logs on disk because the buffers are full. Until R...
Identify Contention The following query determines the miss ratio and the "immediate" miss ratio for redo log latches. Col MISS_RATIO format 999.99Col IMM_MISS_RATIO format 999.99 SELECT substr(ln.na...
Row chaining occurs when a row can't physically fit into an Oracle block. Another block is required to store the remainder of the row. Chaining can cause serious performance problems and is especially...
Oracle provides statistics which relate to the capability of rollbacks to shrink back to an optimal size. To make use of these statistics it is suggested that the following two views be created to red...
Shared pool latch contention can occur when the shared pool is sized too large to be effectively managed. Starting with Oracle version 8.1.6, Oracle implemented improved shared pool management archite...
Just as the architecture of the database buffer cache has changed dramatically from release to release, so too have the effectiveness of the tools Oracle supplies to assist with tuning the database bu...
