Oracle Wait Class Test

When Oracle executes an SQL statement, it is not constantly executing. Sometimes it has to wait for a specific event to happen before it can proceed. For example, if Oracle (or the SQL statement) wants to modify data, and the corresponding database block is not currently in the SGA, Oracle waits for this block to be available for modification. Every such wait event belongs to a class of wait events. The following list describes each of the wait classes.

Wait Class	Description
Administrative	Waits resulting from DBA commands that cause users to wait (for example, an index rebuild)
Application	Waits resulting from user application code (for example, lock waits caused by row level locking or explicit lock commands)
Cluster	Waits related to Real Application Cluster resources (for example, global cache resources such as ‘gc cr block busy’
Commit	This wait class only comprises one wait event - wait for redo log write confirmation after a commit (that is, ‘log file sync’)
Concurrency	Waits for internal database resources (for example, latches)
Configuration	Waits caused by inadequate configuration of database or instance resources (for example, undersized log file sizes, shared pool size)
Idle	Waits that signify the session is inactive, waiting for work (for example, ‘SQL*Net message from client’)
Network	Waits related to network messaging (for example, ‘SQL*Net more data to dblink’)
Other	Waits which should not typically occur on a system (for example, ‘wait for EMON to spawn’)
Scheduler	Resource Manager related waits (for example, ‘resmgr: become active’)
System I/O	Waits for background process IO (for example, DBWR wait for ‘db file parallel write’)
User I/O	Waits for user IO (for example ‘db file sequential read’)

Since wait events are resource-drains and serious performance degraders, administrators need to keep a close eye on these wait classes, figure out how much time the Oracle database server actually spends waiting for each class, and rapidly decipher why, so that measures can be initiated to minimize these events. To achieve this, you can use the Oracle Wait Class test. This test reports the time spent by the Oracle server waiting for events of each wait class, helps identify those wait classes with wait events that have remained active for a long time, and also reveals the number of sessions that have been impacted by the waiting. With the help of the detailed diagnostics of this test, you can also zoom into these sessions and identify the queries that they executed that may have caused wait events to occur; this way, inefficient queries can be isolated.

Target of the test : An Oracle server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for each wait class active on the Oracle database server being monitored.

Configurable parameters for the test
TEST PERIOD - How often should the test be executed Host – The host for which the test is to be configured Port - The port on which the server is listening User – In order to monitor an Oracle database server, a special database user account has to be created in every Oracle database instance that requires monitoring. A Click here hyperlink is available in the test configuration page, using which a new oracle database user can be created. Alternatively, you can manually create the special database user. When doing so, ensure that this user is vested with the select_catalog_role and create session privileges. The sample script we recommend for user creation (in Oracle database server versions before 12c) for eG monitoring is: create user oraeg identified by oraeg create role oratest; grant create session to oratest; grant select_catalog_role to oratest; grant oratest to oraeg; The sample script we recommend for user creation (in Oracle database server 12c) for eG monitoring is: alter session set container=<Oracle_service_name>; create user <user_name>identified by <user_password> container=current default tablespace <name_of_default_tablespace> temporary tablespace <name_of_temporary_tablespace>; Grant create session to <user_name>; Grant select_catalog_role to <user_name>; The name of this user has to be specified here. Password – Password of the specified database user This login information is required to query Oracle’s internal dynamic views, so as to fetch the current status / health of the various database components. Confirm password – Confirm the password by retyping it here. ISPASSIVE – If the value chosen is yes, then the Oracle server under consideration is a passive server in an Oracle cluster. No alerts will be generated if the server is not running. Measures will be reported as “Not applicable" by the agent if the server is not up. SSL- By default, this flag is set to No, as the target Oracle database is not SSL-enabled by default. If the target database is SSL-enabled, then set this flag to Yes. SSL Cipher-This parameter is applicable only if the target Oracle database is SSL-enabled, if not, set this parameter to none. A cipher suite is a set of cryptographic algorithms that are used before a client application and server exchange information over an SSL/TLS connection. It consist of sets of instructions on how to secure a network through SSL (Secure Sockets Layer) or TLS (Transport Layer Security). In this text box, provide a comma-seperated list of cipher suites that are allowed for SSL/TLS connection to the target database. By default, this parameter is set to none. TRUSTSTORE FILE- This parameter is applicable only if the target Oracle database is SSL-enabled, if not, set this parameter to none. TrustStore is used to store certificates from Certified Authorities (CA) that verify and authenticate the certificate presented by the server in an SSL connection. Therefore, the eG agent should have access to the truststore where the certificates are stored to authenticate and connect with the target database and collect metrics. For this, first import the certificates into the following default location <eG_INSTALL_DIR>/lib/security/mytruststore.jks. To know how to import the certificate into the truststore, refer toPre-requisites for monitoring Oracle Cluster. Then, provide the truststore file name in this text box. For example: mytruststore.jks. By default, none is specified against this text box. TRUSTSTORE TYPE-This parameter is applicable only if the target Oracle database is SSL-enabled, if not, set this parameter to none.Specify the type of truststore that contains the certificates for server authentication in this text box. For eg.,JKS. By default, this parameter is set to the value none. TRUSSTORE PASSWORD-This parameter is applicable only if the target Oracle database is SSL-enabled, if not, set this parameter to none. If a Truststore File name is provided, then, in this text box, provide the password that is used to obtain the associated certificate details from the Truststore File. By default, this parameter is set to none. DETAILED DIAGNOSIS – To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option. The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled: The eG manager license should allow the detailed diagnosis capability Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.

Measurements made by the test
Measurement	Description	Measurement Unit	Interpretation
Active sessions:	Indicates the current number of sessions in which events of this wait class are currently active.	Number	A high value indicates that too many sessions are waiting owing to the events of a particular wait class. To know more about these sessions, the wait events that each session triggered, and which query triggered the events, use the detailed diagnosis of this measure. With the help of the detailed metrics, you can quickly isolate the queries that require optimization.
Max wait time:	Indicates the maximum time for which the Oracle server has waited for events of this wait class.	Secs	A high value is indicative of the following: An increase in load (either more users, more calls, or larger transactions) I/O performance degradation (I/O time increases and wait time increases, so DB time increases) Application performance degradation CPU-bound host (foregrounds accumulate active run-queue time, wait event times are artificially inflated) Compare the value of this measure across wait classes to identify which wait class has caused the Oracle database server to wait for the maximum time. You can then use the detailed diagnostics reported by the Active sessions measure to identify which sessions were impacted, and what queries were executed by those sessions to increase wait time. Inefficient queries can thus be identified and optimized to ensure that waiting is eliminated or at least minimized.