Oracle RAC Commits Test

A wait class is a grouping of wait events, and every wait event belongs to a wait class. The main wait classes of the Oracle database server are:

Administrative
Application
Cluster
Commit
Concurrency
idle
Network
Other
Scheduler
System I/O
User I/O

The Commit wait class comprises of only one wait event - wait for redo log write confirmation after a commit (that is, ‘log file sync’ event). Commit is not complete until LGWR (log writer) writes log buffers including commit redo records to log files. In a nutshell, after posting LGWR to write, user or background processes waits for LGWR to signal back with 1 sec timeout. User process charges this wait time as ‘log file sync’ event.

This test reports the number of sessions to each instance, which are waiting for a redo log write confirmation after a commit. This way, the test sheds light on the open sessions to a instance, and the reason for the sessions remaining.

This test is disabled by default. To enable the test, go to the enable / disable tests page using the menu sequence : Agents -> Tests -> Enable/Disable, pick the Oracle RAC as desired Component type, set Performance as the Test type, choose the test from the disabled tests list, and click on the >> button to move the test to the ENABLED TESTS list. Finally, click the Update button.

Note:

This test is applicable for Oracle Clusters with Multi-tenancy i.e., CDB(Container Database) and PDB (Pluggable Database) configuration.

Target of the test : Oracle RAC

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every instance in the monitored Oracle RAC.

Configurable parameters for the test
Parameter	Description
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.
SCAN Name	SCAN stands for Single Client Access Name, it is a feature used in Oracle RAC environments that provide a single name for clients to access any Oracle Database running in the cluster. You can provide SCAN as an alternative to IP/Host Name. If this parameter value is provided, it will be used for connectivity otherwise IP/Hostname will be used.
ORASID	The variable name of the oracle instance.
Service Name	A Service Name exists for the entire Oracle RAC system. When clients connect to an Oracle cluster using the Service Name, then the cluster routes the request to any available database instance in the cluster. By default, the Service Name is set to none. In this case, the test connects to the cluster using the ORASID and pulls out the metrics from that database instance which corresponds to that ORASID. If a valid Service Name is specified instead, then, the test will connect to the cluster using that Service Name, and will be able to pull out metrics from any available database instance in the cluster. To know the Service Name of a cluster, execute the following query on any node in the target cluster: select name, value from v$parameter where name =’service_names’
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
Confirm Password	Confirm the password by retyping it here.
SSL	By default, this flag is set to No, as the target Oracle cluster is not SSL-enabled by default. If the target cluster is SSL-enabled, then set this flag to Yes.
SSL Cipher	This parameter is applicable only if the target Oracle Cluster 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 cluster. By default, this parameter is set to none.
Truststore File	- This parameter is applicable only if the target Oracle Cluster 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 cluster 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 Cluster 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.
Truststore Password	-This parameter is applicable only if the target Oracle Cluster 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.
Keystore File	This parameter is applicable only if the target Oracle Cluster is SSL-enabled, if not, set this parameter to none. Keystore contains the private keys for the certificates that the client can provide to the server upon request. eG agent requires access to the keystore where client certificate is stored to send that to the server so that the server validates the certificate against the one contained in its trustore. For this purpose, first create the client certificate in the following default location EG_INSTALL_DIR/jre/lib/security/mykeystore.jks. Then, provide the keystore file name in this text box. For example: mykeystore.jks. By default, none is specified against this text box.
Keystore Password	This parameter is applicable only if the target Oracle Cluster is SSL-enabled, if not, set this parameter to none. If a Keystore File name or file path is provided, then, in this text box, provide the password that is used to obtain the associated certificate details from the Keystore File.
Confirm Password	Confirm the Password for Keystore by retyping it here.
DD Frequency	Refers to the frequency with which detailed diagnosis measures are to be generated for this test. The default is 1:1. This indicates that, by default, detailed measures will be generated every time this test runs, and also every time the test detects a problem. You can modify this frequency, if you so desire. Also, if you intend to disable the detailed diagnosis capability for this test, you can do so by specifying none against DD frequency.
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
Number of Sessions:	Indicates the number of sessions to this instance that are waiting for redo log confirmation after commit.	Number	A steady increase in the value of this measure is a cause of concern, as it indicates the following: Many sessions are forced to stay open owing to the commit wait events, and this may cause a session overload; Many “log file sync” wait events are occuring, causing the performance of the Oracle RAC to deteriorate. The root cause for ‘log file sync’ waits are as follows: LGWR is unable to complete writes fast enough - this could be because, the disk I/O performance to log files is not good enough or, the LGWR is starving for CPU resources or, the LGWR paged out due to memory starvation issues or, due to file system or unix buffer cache limitations LGWR is unable to post the processes fast enough, due to excessive commits. IMU undo/redo threads LGWR is suffering from other database contention such as enqueue waits or latch contention Various bugs Use the detailed diagnosis of this measure to view the details of the sessions affected by log file sync waits.