Welcome
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 HCL® 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.
Effect of configuration on memory utilization
The combination of operating-system and Informix® configuration parameters can affect memory utilization.
Configuration parameters that affect memory utilization
A large number of configuration parameters in the ONCONFIG file affect memory utilization and performance.
The SHMVIRT_ALLOCSEG configuration parameter and memory utilization
The SHMVIRT_ALLOCSEG configuration parameter specifies a threshold at which the database server should allocate memory. This configuration parameter also defines an alarm event security-code that is activated if the server cannot allocate the new memory segment, thus ensuring that the database server never runs out of memory.

HCL Informix® V15.0.0 documentation
Welcome to the documentation for HCL Informix® 15.0.0 and related client tools and products.
Product overview
HCL Informix® is a fast and scalable database server that manages traditional relational, object-relational, and dimensional databases. Its small footprint and self-managing capabilities are suited to embedded data-management solutions.
Installing
These topics describe how to install HCL Informix® database servers, client products, and modules.
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 HCL® Informix® Administrator's Guide provides the information required to administer HCL Informix.
  - Administrator's Reference
    The HCL® 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 HCL® Informix® DB-Access User's Guide describes how to use the utility to access, modify, and retrieve information from HCL 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 HCL® 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.
      - Shared memory
        You must configure adequate shared-memory resources for the database server in your operating system. Insufficient shared memory can adversely affect performance.
      - Configuration parameters that affect memory utilization
        A large number of configuration parameters in the ONCONFIG file affect memory utilization and performance.
        Setting the size of the buffer pool, logical-log buffer, and physical-log buffer
        The values that you specify for the BUFFERPOOL, DS_TOTAL_MEMORY, LOGBUFF, and PHYSBUFF configuration parameters depend on the type of applications that you are using (OLTP or DSS) and the page size.
        The LOCKS configuration parameter and memory utilization
        The LOCKS configuration parameter specifies the initial size of the lock table. The lock table holds an entry for each lock that a session uses. Each lock uses 120 bytes within a lock table. You must provide for this amount of memory when you configure shared memory.
        The RESIDENT configuration parameter and memory utilization
        The RESIDENT configuration parameter specifies whether shared-memory residency is enforced for the resident portion of database server shared memory. This configuration parameter works only on computers that support forced residency.
        The SHMADD and EXTSHMADD configuration parameters and memory utilization
        The SHMADD configuration parameter specifies the size of each increment of shared memory that the database server dynamically adds to the virtual portion. The EXTSHMADD configuration parameter specifies the size of a virtual-extension segment that is added when user-defined routines or routines run in user-defined virtual processors. Trade-offs are involved in determining the size of an increment.
        The SHMTOTAL configuration parameter and memory utilization
        The SHMTOTAL configuration parameter places an absolute upper limit on the amount of shared memory that an instance of the database server can use.
        The SHMVIRTSIZE configuration parameter and memory utilization
        The SHMVIRTSIZE parameter specifies the size of the virtual portion of shared memory to allocate when you start the database server. The virtual portion of shared memory holds session- and request-specific data as well as other information.
        The SHMVIRT_ALLOCSEG configuration parameter and memory utilization
        The SHMVIRT_ALLOCSEG configuration parameter specifies a threshold at which the database server should allocate memory. This configuration parameter also defines an alarm event security-code that is activated if the server cannot allocate the new memory segment, thus ensuring that the database server never runs out of memory.
        The STACKSIZE configuration parameter and memory utilization
        The STACKSIZE configuration parameter indicates the initial stack size for each thread. The database server assigns the amount of space that this parameter indicates to each active thread. This space comes from the virtual portion of database server shared memory. You can reduce the amount of shared memory that the database server adds dynamically.
      - Configure and monitor memory caches
        The database server uses caches to store information in memory instead of performing a disk read or another operation to obtain the information. These memory caches improve performance for multiple queries that access the same tables. You can set some configuration parameters to increase the effectiveness of each cache. You can view information about memory caches by running onstat commands.
      - Session memory
        The database server uses the virtual portion of shared memory mainly for user sessions. Most of the memory that each user session allocates is for SQL statements. You can determine which session and which statements are using large amounts of memory. If necessary, you can set the SESSION_LIMIT_MEMORY configuration parameter to limit the amount of memory available to a session.
      - Data-replication buffers and memory utilization
        Data replication requires two instances of the database server, a primary one and a secondary one, running on two computers. If you implement data replication for your database server, the database server holds logical-log records in the data-replication buffer before it sends them to the secondary database server.
      - Memory latches
        The database server uses latches to control access to shared memory structures such as the buffer pool or the memory pools for the SQL statement cache. You can obtain statistics on latch use and information about specific latches. These statistics provide a measure of the system activity.
      - Encrypted values
        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.
    - 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.
    - 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.
- Backup and Restore Guide
  The HCL® Informix® Backup and Restore Guide describes how to use the HCL Informix 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 describes the concepts of data replication using HCL Informix® Enterprise Replication, including how to design your replication system, as well as administer and manage data replication throughout your enterprise.
Migrating and upgrading
You can upgrade to the 15.0.0 release of HCL Informix® or migrate from other database servers to Informix. Upgrading is an in-place migration method that uses your existing hardware and operating system software. Some changes to the Informix database server can affect upgrading from a previous release.
Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
Embedding Informix®
When you embed HCL Informix®, you can use enterprise-class high-availability and high performance with embeddability features such as easy programmability, a small disk and memory footprint, and silent deployment.
Extending Informix®
Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix includes many built-in extensions that are fully integrated in the database server. Informix also provides modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix.
Data warehousing
In addition to designing and implementing Informix® dimensional databases, you can use tools to create data warehouse applications and optimize your data warehouse queries.
Designing databases
The first step in creating a relational database is to construct a data model, which is a precise, complete definition of the data you want to store. After you prepare your data model, you must implement it as a database and tables. To implement your data model, you first select a data type for each column and then you create a database and tables and populate the tables with data. You can also implement fragmentation strategies and control access to your data.
JSON compatibility
You can use the popular JSON-oriented query language created by MongoDB to interact with data stored in HCL Informix®.
Security
You can secure your Informix® database server and the data that is stored in your Informix databases. You can encrypt data, secure connections, control user privileges and access, and audit data security.
SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Troubleshooting HCL Informix®
Several troubleshooting techniques, tools, and resources are available for resolving problems that you encounter in your HCL Informix® database server environment.

The SHMVIRT_ALLOCSEG configuration parameter and memory utilization

The SHMVIRT_ALLOCSEG configuration parameter specifies a threshold at which the database server should allocate memory. This configuration parameter also defines an alarm event security-code that is activated if the server cannot allocate the new memory segment, thus ensuring that the database server never runs out of memory.

When you set the SHMVIRT_ALLOCSEG configuration parameter, you must:

Specify the percentage of memory used or the whole number of kilobytes remaining on the server. You cannot use negative values and values between 0 and .39.
Specify the alarm event-security code, which is a value ranging from 1 (not noteworthy) to 5 (fatal). If you do not specify an event-security code, the server sets the value to 3, which is the default value.

Example 1:

SHMVIRT_ALLOCSEG 3000, 4

This specifies that if the database serve has 3000 kilobytes remaining in virtual memory and additional kilobytes of memory cannot be allocated, the server raises an alarm level of 4.

Example 2:

SHMVIRT_ALLOCSEG .8, 4

This specifies that if the database server has twenty percent remaining in virtual memory and additional kilobytes of memory cannot be allocated, the server raises an alarm level of 4.