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Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
System administration
These topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
Performance Guide
The Informix® Performance Guide describes how to configure and operate your HCL Informix database server to improve overall system throughput and to improve the performance of SQL queries.
Fragmentation guidelines
One of the most frequent causes of poor performance in relational database systems is contention for data that resides on a single I/O device. Proper fragmentation of high-use tables can significantly reduce I/O contention. These topics discuss the performance considerations that are involved when you use table fragmentation.
Improve the performance of operations that attach and detach fragments
When you use ALTER FRAGMENT ATTACH and DETACH statements to add or remove a large amount of data in a very large table, you can take steps to improve the performance of the ATTACH and DETACH operations.
Improving ALTER FRAGMENT ATTACH performance
You can take advantage of the performance optimizations for the ALTER FRAGMENT ATTACH statement if your database meets certain requirements.
Indexes on attached tables
The database server tries to reuse the indexes on the attached tables as fragments of the resultant index. However, the corresponding index on the attached table might not exist or might not be usable due to disk-format mismatches. In these cases, it might be faster to build an index on the attached tables rather than to build the entire index on the resultant table.

Administering
In addition to administering the database server, you can tune performance, replicate data, and archive data.
- System administration
  These topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL Informix® database servers.
  - List of utilities
    HCL Informix® includes utilities and applications that you can use to perform administrative tasks and capture information about configuration and performance.
  - Administrator's Guide
    The Informix® Administrator's Guide provides the information required to administer HCL Informix.
  - Administrator's Reference
    The Informix® Administrator's Reference includes comprehensive descriptions of HCL Informix configuration parameters, the system-monitoring interface (SMI) tables in the sysmaster database, the syntax of database server utilities such as onmode and onstat, logical-log records, disk structures, event alarms, and unnumbered error messages.
  - DB-Access User's Guide
    The Informix® DB-Access User's Guide describes how to use the DB-Access utility to access, modify, and retrieve information from Informix database servers.
  - High-Performance Loader User's Guide
    The describes how to use the HCL Informix® to load and unload large quantities of data efficiently to or from Informix databases.
  - Performance Guide
    The Informix® Performance Guide describes how to configure and operate your HCL Informix database server to improve overall system throughput and to improve the performance of SQL queries.
    - Performance basics
      Performance measurement and tuning issues and methods are relevant to daily database server administration and query execution.
    - Performance monitoring and the tools you use
      You can use performance monitoring tools to create a performance history, to monitor database resources at scheduled times, or to monitor ongoing transaction or query performance.
    - Effect of configuration on CPU utilization
      The combination of operating-system and Informix® configuration parameters can affect CPU utilization. You can change the settings of the Informix configuration parameters that directly affect CPU utilization, and you can adjust the settings for different types of workloads.
    - Effect of configuration on memory utilization
      The combination of operating-system and Informix® configuration parameters can affect memory utilization.
    - Table performance considerations
      Some performance issues are associated with unfragmented tables and table fragments.
    - Boosted Partition Free Space Caches (PFSC)
    - Indexes and index performance considerations
      Informix® provides several types of indexes. Some performance issues are associated with indexes.
    - Locking
      The database server uses locks, which can affect concurrency and performance. You can monitor and administer locks.
    - Fragmentation guidelines
      One of the most frequent causes of poor performance in relational database systems is contention for data that resides on a single I/O device. Proper fragmentation of high-use tables can significantly reduce I/O contention. These topics discuss the performance considerations that are involved when you use table fragmentation.
      - Planning a fragmentation strategy
        You can decide on a fragmentation goal for your database and devise a strategy to meet that goal.
      - Distribution schemes
        After you decide whether to fragment table rows, index keys, or both, and you decide how the rows and keys should be distributed over fragments, you can decide on a scheme to implement this distribution. Informix® supports random distribution among fragments and value-based distribution among fragments.
      - Strategy for fragmenting indexes
        When you fragment a table, the indexes that are associated with that table are fragmented implicitly, according to the distribution scheme that you use, except for the round-robin fragmentation scheme when automatic location is enabled. Indexes on tables that use the round-robin distribution scheme are not fragmented when the AUTOLOCATE configuration parameter or environment option is set to a positive integer. You can use the FRAGMENT BY clause of the CREATE INDEX statement to fragment the index on any table.
      - Strategy for fragmenting temporary tables
        You can fragment an explicit temporary table across dbspaces that reside on different disks.
      - Distribution schemes that eliminate fragments
        Fragment elimination is a database server feature that reduces the number of fragments involved in a database operation. This capability can improve performance significantly and reduce contention for the disks on which fragments reside.
      - Improve the performance of operations that attach and detach fragments
        When you use ALTER FRAGMENT ATTACH and DETACH statements to add or remove a large amount of data in a very large table, you can take steps to improve the performance of the ATTACH and DETACH operations.
        Improving ALTER FRAGMENT ATTACH performance
        You can take advantage of the performance optimizations for the ALTER FRAGMENT ATTACH statement if your database meets certain requirements.
        Distribution schemes for reusing indexes
        You can use one of three distribution schemes that allow the attach operation of the ALTER FRAGMENT statement to reuse existing indexes.
        Ensuring no data movement when you attach a fragment
        You can ensure there is no data movement when you attach a fragment by establishing identical check constraint expressions and verifying that fragment expressions are not overlapping.
        Indexes on attached tables
        The database server tries to reuse the indexes on the attached tables as fragments of the resultant index. However, the corresponding index on the attached table might not exist or might not be usable due to disk-format mismatches. In these cases, it might be faster to build an index on the attached tables rather than to build the entire index on the resultant table.
        Example for situation when corresponding index does not exist
        When a table does not have an index on a column that can serve as the fragment of the resultant index, the database server estimates the cost of building the index fragment for the column, compares this cost to rebuilding the entire index for all fragments on the resultant table, and chooses the index build with the least cost.
        Example for situation when index on table is not usable
        When the index on a table is not usable, the database server estimates the cost of building the index fragment, compares this cost to rebuilding the entire index for all fragments on the resultant table, and chooses the index build with the least cost.
        Improving ALTER FRAGMENT DETACH performance
        You can improve the performance of ALTER FRAGMENT DETACH statements by formulating appropriate distribution schemes for your table and index fragments and by eliminating the index build during the execution of ALTER FRAGMENT DETACH statements.
        Forcing out transactions when altering table fragments
        You can enable the server to force out transactions that have opened or hold locks on the target table of an ALTER FRAGMENT ON TABLE operation in a logging database. Users holding the DBA access privilege can do this by enabling the FORCE_DDL_EXEC session environment option of the SET ENVIRONMENT statement.
      - Monitoring Fragment Use
        Once you determine a fragmentation strategy, you can monitor fragmentation.
    - Queries and the query optimizer
      These topics describe query plans, explain how the database server manages query optimization, and discuss factors that you can use to influence the query plan. These topics also describe performance considerations for SPL routines, the UDR cache, and triggers.
    - Optimizer directives
      Optimizer directives are comments that tell the query optimizer how to execute a query. You can use optimizer directives to improve query performance.
    - Parallel database query (PDQ)
      You can manage how the database server performs PDQ and you can monitor the resources that the database server uses for PDQ.
    - Improving individual query performance
      You can test, monitor, and improve queries.
    - Appendix
  - SNMP Subagent Guide
    The describes the Simple Network Management Protocol (SNMP) and the software that you need to use SNMP to monitor and manage HCL Informix® database servers and databases.
  - InformixHQ Guide
    InformixHQ is a modern web console for visualizing, monitoring, and managing your Informix server instances. It is purpose built for ease-of-use, scaling out, and optimizing DevOps needs. It provides critical performance management capabilities, monitoring how key performance metrics are changing over time and tracking how efficiently Informix is running your workload even when you’ve stepped away from your screen. Its monitoring system feeds directly into a customizable alerting system so you can be immediately alerted via email, Twilio, or PagerDuty whenever an issue occurs on one of your Informix database server instances. InformixHQ is designed to be scalable to efficiently manage and monitor as many Informix database server instances as you need. Moreover, it's a tool that can be shared by the DBAs, the app developers, the ops engineers, and management and accessed from any desktop, laptop, or mobile device. InformixHQ is the centralized hub for graphical monitoring, alerting, and administration of your Informix database servers.
- Backup and Restore Guide
  The Informix® Backup and Restore Guide describes how to use the Informix ON-Bar and ontape utilities to back up and restore database server data. These utilities enable you to recover your databases after data is lost or becomes corrupted due to hardware or software failure or accident.
- Enterprise Replication
  The HCL® Informix® Enterprise Replication Guide describes the concepts of data replication using Informix Enterprise Replication, including how to design your replication system, as well as administer and manage data replication throughout your enterprise.

Indexes on attached tables

The database server tries to reuse the indexes on the attached tables as fragments of the resultant index. However, the corresponding index on the attached table might not exist or might not be usable due to disk-format mismatches. In these cases, it might be faster to build an index on the attached tables rather than to build the entire index on the resultant table.

Informix® estimates the cost to create the whole index on the resultant table. The server then compares this cost to the cost of building the individual index fragments for the attached tables and chooses the index build with the least cost.

Automatically Gathered Statistics for New Indexes

When the CREATE INDEX statement runs successfully, with or without the ONLINE keyword, Informix® automatically gathers the following statistics for the newly created index:

Index-level statistics, equivalent to the statistics gathered in the UPDATE STATISTICS operation in LOW mode, for all types of indexes, including B-tree, Virtual Index Interface, and functional indexes.
Column-distribution statistics, equivalent to the distribution generated in the UPDATE STATISTICS operation in HIGH mode, for a non-opaque leading indexed column of an ordinary B-tree index. The resolution of the HIGH mode is 1.0 for a table size that is less than 1 million rows and 0.5 for higher table sizes. Tables with more than 1 million rows have a better resolution because they have more bins for statistics.

The automatically gathered distribution statistics are available to the query optimizer when it designs query plans for the table on which the new index was created.

Run UPDATE STATISTICS Before Attaching Tables

To ensure that cost estimates are correct, you should execute the UPDATE STATISTICS statement on all of the participating tables before you attach the tables. The LOW mode of the UPDATE STATISTICS statement is sufficient to derive the appropriate statistics for the optimizer to determine cost estimates for rebuilding indexes.

For more information about using the UPDATE STATISTICS statement, see the Informix® Guide to SQL: Syntax.