Oracle Data File I/O Test

If an Oracle datafile is able to process I/O requests to it quickly, it is a sign of the good health of the Oracle database server. On the other hand, any slowdown in IOPS could indicate a serious processing bottleneck on the server, probably caused by a poor indexing engine or badly structured tables in a datafile. Administrators should hence continuously track the I/O requests to every datafile on the Oracle database server, identify the type of requests received – i.e., whether single block or multi-block I/O requests - and measure the time taken by that datafile to process each type of request. For this purpose, you can run the Oracle Data File I/O test.

This test auto-discovers the datafiles on the Oracle database server and reports the time taken by each datafile to process single block and multiblock I/O requests. In the process, I/O processing bottlenecks can be detected and the datafiles affected can be identified.

Target of the test : An Oracle 12c server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every datafile on the Oracle server.

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. listener name – Specify the Oracle listener name. By default, this will be the same as the Oracle SID. 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.

Measurements made by the test
Measurement	Description	Measurement Unit	Interpretation
Multiblock read time:	Indicates the time taken by this datafile to service multiblock I/O requests during the last measurement period.	Secs/Read	Multiblock I/O read means reading multiple database blocks with a single operating system READ call. Typically, a database block is 8 KB. A single block read call results in one of these 8 KB blocks read from the datafile. Where a lot of data is to be read, it would be less efficient and more resource-intensive to read single blocks of data of 8KB each when the underlying I/O system is capable of reading say, 1 MB in one read. Oracle therefore issues a multiblock I/O and requests 1MB worth of block (128 8kb blocks) in one system READ call rather than 128 individual requests and therefore speeds up performance of the I/O requests. A very high value of this measure could indicate a bottleneck when processing multiblock read requests to a particular datafile. Compare the value of this measure across files to accurately identify that datafile from which multiple blocks of data were read from most slowly. In the event of high latency when processing read requests, you can do one/more of the following to clear the processing bottleneck: Create tables and indexes in separate tablespaces. Create datafiles across multiple disks. Create table partitions across multiple datafiles.
Singleblock read time:	Indicates the time taken for singleblock reads from this datafile during the last measurement period.	Secs/read	Typically, a database block is 8 KB. A single block read call results in one of these 8 KB blocks read from the datafile. Where a lot of data is to be read, it would be less efficient and more resource-intensive to read single blocks of data of 8KB each when the underlying I/O system is capable of reading say, 1 MB in one read. A very high value of this measure could indicate a bottleneck when processing single block write requests to a particular datafile. Compare the value of this measure across files to accurately identify that datafile from which a single block of data was read most slowly.
Multiblock write time:	Indicates the time taken for multiblock writes into this datafile during the last measurement period.	Secs/write	Multiblock I/O write means writing multiple database blocks to a datafile with a single operating system WRITE call. A very high value of this measure could indicate a bottleneck when processing multiblock write requests to a particular datafile. Compare the value of this measure across files to accurately identify that datafile to which multiple blocks of data were written most slowly. If the write latency is very high, you can do one/more of the following to clear the processing bottleneck: Create tables and indexes in separate tablespaces. Create datafiles across multiple disks. Create table partitions across multiple datafiles.
Singleblock write time:	Indicates the time taken for singleblock writes to this datafile during the last measurement period.	Secs/write	In case of a singleblock write, a write call results in a single 8KB block being written into the datafile. If a lot of data is to be written to a datafile, single block writes can significantly increase I/O processing overheads and related resource costs. A very high value of this measure could indicate a bottleneck when processing single block write requests to a particular datafile. Compare the value of this measure across files to accurately identify that datafile to which a single block of data was written most slowly.
Sync read latency:	Indicates the average latency for singleblock synchronous reads for single request since last test cycle on each datafile.	Msecs/request	If there is a high latency for critical data files, you may want to consider relocating these files to improve their service time.
IO time since last measure:	Indicates the time taken by IOPS on this datafile during the last measurement period.	Secs	A high value could indicate a processing bottleneck with the datafile. Compare the value of this measure across datafiles to identify that datafile to which the read/write requests take too long to be serviced.