What are Materialized Views Oracle Materialized Views or MVs are a good option for data warehousing and replication. MVs based on inner/outer equijoin can be refreshed on-demand or periodically if desired. MVs that are based on sub-queries on remote tables support bi-directional replication. An MV includes a query that is transparent to the user, and […]
What are Local and Global Indexes in Oracle Database
Background information In a local index, all keys in a particular index partition refer only to rows stored in a single underlying table partition. A local index is created by specifying the LOCAL attribute. In a global partitioned index, the keys in a particular index partition may refer to rows stored in multiple underlying table […]
WITH Clause in ORACLE
As per Oracle Documentation, the WITH query_name clause lets you assign a name to a subquery block. You can then reference the subquery block multiple places in the query by specifying the query name. Oracle Database optimizes the query by treating the query name as either an inline view or as a temporary table. You […]
What is the difference between PRIMARY Key and UNIQUE Key
The primary key is used to ensure that all values in a column are not null and unique. This key combines the unique and not null constraint properties into one key. This type of key can be applied to any data type and is used to avoid missing and duplicate data. You can only have […]
Oracle OS watcher (OSWatcher) – Understanding oswmpstat
Oracle provides a collection of scripts that gather and store metrics for CPU, memory, disk, and network usage. The OSWatcher tool suite automates the gathering of statistics using tools such as top, vmstat, iostat, mpstat, netstat, and traceroute. The general file format for the oswmpstat data is: [node_name]_mpstat_YY.MM.DD:HH24.dat These files will contain output from the […]
Oracle OS watcher (OSWatcher) – Understanding oswiostat
Oracle provides a collection of scripts that gather and store metrics for CPU, memory, disk, and network usage. The OSWatcher tool suite automates the gathering of statistics using tools such as top, vmstat, iostat, mpstat, netstat, and traceroute. The general file format for the oswiostat data is: [node_name]_iostat_YY.MM.DD:HH24.dat These files will contain output from the […]
How to Start and Stop OSWatcher
OSWatcher (oswbb) is a collection of UNIX shell scripts intended to collect and archive operating system and network metrics to aid support in diagnosing performance issues. As a best practice, all customers should install and run OSWatcher on every node that has a running Oracle instance. In the case of a performance issue, Oracle support […]
iotop Command Examples in Linux
To get a live view of the input and output, or short I/O, bandwidth usage of your system, type iotop. iotop needs to be started with the root user. You can use iotop, for example, to learn how fast your hard disk can read and write, then press the q key to exit. Please read […]
Basic Commands to Troubleshoot Performance Issues in Linux
Following is the list of OS commands apart from basic commands that are useful in diagnosing the problems at OS end causing the slow performance. Please note that all the commands mentioned above are tested in a Linux environment only. If you are ready to track down your performance problems, here are some tools to […]
How to Determine Which Process is Writing to Disk in Linux
It’s also possible on Linux to get per process I/O statistics, so you can see exactly who is reading and writing heavily, using a program named iotop. iotop needs to be started with the root user. You can use iotop, for example, to learn how fast your hard disk can read and write, then press […]