Here is part -4 of the series Top 100 Hyperion Essbase Interview questions
76) How to make Essbase application read-write and read only in case backup fails in that stage
Archive mode (Essbase application in read only mode) by using of below command we can achieve that
alter database dbname begin archive
Essbase application read – write mode we can achieve that by using of below command
alter database dbname end archive
77) How can we backup a block storage database?
- a) put the application in read only mode
- b) Take a archive of the whole application which contains all the files.
- c) put the application back in read write mode
78) What is dense restructuring?
If a member of a dense dimension is moved, deleted, or added, Essbase restructures the blocks in the data files and creates new data files. When Essbase restructures the data blocks, it regenerates the index automatically so that index entries point to the new data blocks. Empty blocks are not removed. Essbase marks all restructured blocks as dirty, so, after a dense restructure you must recalculate the database. Dense restructuring, the most time-consuming of the restructures, can take a long time to complete for large databases.
79) What is sparse restructuring?
If a member of a sparse dimension is moved, deleted, or added, Essbase restructures the index and creates new index files. Restructuring the index is relatively fast; the time required depends on the index size.
80) What is Outline-only restructure
If a change affects only the database outline, Essbase does not restructure the index or data files. Member name changes, creation of aliases, and dynamic calculation formula changes are examples of changes that affect only the database outline.
81) How Essbase performs Sparse restructuring?
When Essbase does a sparse restructure (restructures only the index), it uses the following files:
To perform a sparse restructure, Essbase does the following:
1 Renames the dbname.esm file to dbname.esr.
2 Renames the essxxxxx.ind files to essxxxxx.inm.
82) What is intelligent calc? Why should I care?
When you perform a full database calculation, Essbase marks which blocks have been calculated. If you then load a subset of data, you can calculate only the changed data blocks and their ancestors. This selective calculation process is intelligent calculation.
By default, intelligent calculation is turned on. You can change the default setting in the essbase.cfg file or on a script-by-script basis with the SETUPDATECALC OFF command.
Intelligent calculation is based on data-block marking, when intelligent calculation is active, during the normal processes, within the index file, blocks are marked clean or dirty.
Clean Blocks—Blocks that don’t require calculation
Dirty Blocks — Blocks that require calculation.
When intelligent calculation is active, during calculation, Essbase looks for only dirty blocks.
83) How to optimize the data loads in BSO cube?
BSO load process is quite complex process. Following action items can speed the data load in BSO
a) Positioning Data in the Same Order as the Outline
b) Loading from Essbase Server
c) Managing Parallel Data Load Processing
d) Grouping Sparse Member Combinations
e) Making the Data Source as Small as Possible
84) Explain the working of each of the tablespace in ASO cube?
85) What is the use of OPMN in Essbase?
Oracle Process Manager and Notification server (Oracle Process Manager and Notification
Server) enables you to monitor and control the Essbase Agent process. You add Essbase Agent information to the opmn.xml file to enable OPMN to start, stop, and restart the agent using the OPMN command line interface. OPMN can automatically restart the Essbase Agent when it became unresponsive, terminates unexpectedly, or becomes unreachable as determined by ping and notification operations
86) What is active-active clustering?
Active-active Essbase clusters is the cluster of Essbase .it support high availability and load balancing. So, all the Essbase nodes are serving the request. An active-active Essbase cluster supports read-only operations on the databases and should be used only for reporting. Because active-active Essbase clusters do not support data write-back or outline modification, and they do not manage database replication tasks such as synchronizing the changes in one database across all databases in the cluster, they do not support Planning.
87) what is active-passive clustering?
An active-passive Essbase cluster consists of two Essbase instances, one on each node that share a common storage for configuration and data. Storage is shared across two computers which removes the need for the administrator to synchronize storage, as well as the constraint of read-only support (as is the case with Essbase active-active clusters in Provider Services). Essbase uses database tables to ensure that only one agent and its associated servers are active to avoid data corruptions on writes. During installation and configuration, a table is created to hold information on configuration and application data existing in the cluster.
Active-passive Essbase clusters do not use any file-system locking (that is, essbase.lck files).
Some of the feature
- a) Active-passive Essbase clusters support failover with write-back to databases.
- b) Active-passive Essbase clusters do not support load-balancing.
- c) An active-passive Essbase cluster can contain only two Essbase servers.
88) What is split brain problem in Essbase clusters?
split-brain situation can occur when both instances in an active-passive clustered environment think they are “active” and are unaware of each other, which violates the basic premise of active-passive clustering (One node being active). Situations where split-brain can occur include network outages or partitions. Such situation can result in corruption
89) How Essbase resolved the split-brain problem?
Essbase failover uses a leasing mechanism to solve the problem of split-brain
90) How Leasing mechanism works in Essbase?
An Essbase process acquires a lease on a specified shared resource or set of resources upon startup; it renews the lease periodically and surrenders the lease upon termination.
This lease establishes the process as the primary service provider and grants the right to update the specified set of shared resources, service client requests, and spawn processes.
Essbase servers can acquire leases if and only if its authorizing agent has a current lease.
91) How Leases are Implemented internally in Essbase?
Essbase failover implements a leasing mechanism using a centralized relational database to store, update, and retrieve information about the following:
- a) Shared resources
- b) Lease ownership
- c) Lease validity
92) How to stop/start Essbase server?
We start/stop Essbase server using OPMN (Oracle Process Manager). Upon Essbase installation, it registers Essbase Server for OPMN. OPMN manages the Essbase Agent, which manages the Essbase Server. Essbase Server start and stop scripts redirect to OPMN
93) What are these executable Essbase.exe and esssvr.exe in Windows?
94) What does Essbase security file Contains? Where is, it located?
Essbase.sec is an important file for Essbase server functioning.
Essbase is EPM System security mode (Shared services)
Calculation script access
Users and Groups details
Application and Database access type
Application and database properties, including substitution variables and DISKVOLUMES settings
Passwords are not stored in Security files as they are stored in shared services.
Essbase is in native security mode
Stores all information about users, groups, passwords, permissions, filters, applications, databases and corresponding directories
Essbase security file is located in Arborpath/bin directory
95) How to restore the Essbase security file after corruption?
- a) Stop the Essbase services
- b) Copy the essbase_timestamped.bak file from the same arborpath/bin folder and rename it to essbase.sec
- c) Restart the essbase services
Note : Each time essbase server restarts, a backup copy of sec file is created and named as essbase.bak file
96) What is maxl ?
Maxl is a multidimensional database access language that is part of Essbase – Servers provides a flexible way to automate Essbase administration and maintenance tasks
97) What is ARBORPATH?
ARBORPATH is an environment variable which define the home directory for the Essbase – Server.It contain two main directories
|app||The app directory location where Essbase application files (as they are created) and
sample applications and databases (provided with Essbase) are stored.
|Bin||The bin directory location where Essbase configuration setting (essbase.cfg) and
security (essbase.sec and essbase_timestamp.bak) files (as they are created) are
98) What is Essbase exception logs (.xcp)?
If an Essbase Server, an application, or a database shuts down abnormally and cannot restart, Essbase Server generates an exception log to help troubleshoot the problem. The location of the exception log depends on which component shut down abnormally and the amount of information that Essbase Server had available at the time
99) What are transaction in Essbase?
When a database is in read/write mode, Essbase considers every update request to the server (such as a data load, a calculation, or a statement in a calculation script) as a transaction. Essbase tracks information about transactions in a transaction control file (dbname.tct).The transaction control file contains an entry for each transaction and tracks the current state of each transaction (Active, Committed, or Aborted).
100) How to restore Essbase application?
We need to replace the files on disk with the corresponding files from backup to restore a database, . The application should be stopped, unless you are restoring from an export file. In that case, ensure the application is not accepting client connections.