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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.
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.
Time costs of a query
You can adjust a few, but not all, of the response-time effects of actions that the database server performs when processing a query.
GLS functionality costs
Sorting or indexing certain data sets can degrade performance.

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.
    - 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.
      - The query plan
        The query optimizer evaluates the different ways in which a query might be performed and determines the best way to select the requested data. During this evaluation, the optimizer formulates a query plan to fetch the data rows that are required to process a query.
      - Factors that affect the query plan
        When the optimizer determines the query plan, it assigns a cost to each possible plan and then chooses the plan with the lowest cost. The optimizer analyzes several factors to determine the cost of each query plan.
      - Time costs of a query
        You can adjust a few, but not all, of the response-time effects of actions that the database server performs when processing a query.
        Memory-activity costs
        The database server can process only data in memory. It must read rows into memory to evaluate those rows against the filters of a query. After the server finds rows that satisfy those filters, it prepares an output row in memory by assembling the selected columns.
        Sort-time costs
        A sort requires in-memory work as well as disk work. The in-memory work depends on the number of columns that are sorted, the width of the combined sort key, and the number of row combinations that pass the query filter. You can reduce the cost of sorting.
        Row-reading costs
        When the database server needs to examine a row that is not already in memory, it must read that row from disk. The database server does not read only one row; it reads the entire page that contains the row. If the row spans more than one page, it reads all of the pages.
        Sequential access costs
        Disk costs are lowest when the database server reads the rows of a table in physical order.
        Nonsequential access costs
        The disk-access time is much higher when a disk device reads table pages nonsequentially than when it reads that same table sequentially.
        Index lookup costs
        The database server incurs additional costs when it finds a row through an index. The index is stored on disk, and its pages must be read into memory with the data pages that contain the desired rows.
        In-place ALTER TABLE costs
        For certain conditions, the database server uses an in-place alter algorithm to modify each row when you execute an ALTER TABLE statement. After the alter table operation, the database server inserts rows using the latest definition. If your query accesses rows that are not yet converted to the new table definition, you might notice a slight degradation in the performance of your individual query, because the database server reformats each row in memory before it is returned.
        View costs
        A complex view could run more slowly than expected.
        Small-table costs
        A table is small if it occupies so few pages that it can be retained entirely in the page buffers. Operations on small tables are generally faster than operations on large tables.
        Data-mismatch costs
        An SQL statement can encounter additional costs when the data type of a column that is used in a condition differs from the definition of the column in the CREATE TABLE statement.
        Encrypted-value costs
        An encrypted value uses more storage space than the corresponding plain-text value because all of the information needed to decrypt the value except the encryption key is stored with the value.
        GLS functionality costs
        Sorting or indexing certain data sets can degrade performance.
        Network-access costs
        Moving data over a network imposes delays in addition to those you encounter with direct disk access.
      - Optimization when SQL is within an SPL routine
        If an SPL routine contains SQL statements, the database server optimizes and executes the SQL within the SPL routine.
      - Trigger execution
        A trigger is a database object that automatically executes one or more SQL statements (the triggered action) when a specified data manipulation language operation (the triggering event) occurs. You can define one or more triggers on a table to execute after a SELECT, INSERT, UPDATE or DELETE triggering event.
    - 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.

GLS functionality costs

Sorting or indexing certain data sets can degrade performance.

For information about the performance degradation that occurs from indexing some data sets, see Searching for NCHAR or NVARCHAR columns in an index.

If you do not need a non-ASCII collation sequence, use the CHAR and VARCHAR data types for character columns whenever possible. Because CHAR and VARCHAR data require simple value-based comparison, sorting and indexing these columns is less expensive than for non-ASCII data types (NCHAR or NVARCHAR, for example).

For more information about other character data types, see the Informix® GLS User's Guide.