Limits in Informix

This topic lists the system-level and table-level parameter limits, the system defaults, and the access capabilities of Informix®.

System-Level Parameter Limits

Table 1. System-level parameter limits
System-Level Parameters Maximum Capacity per Computer System
HCL Informix systems per computer (Dependent on available system resources) 255
Maximum number of accessible remote sites Machine specific
Maximum virtual shared memory segment (SHMVIRTSIZE) 2GB (32-bit platforms) or 4TB (64-bit platforms)
Maximum number of Informix shared memory segments 1024
Maximum address space UNIX: Machine specific

Windows: 2.7 GB if 4-gigabyte tuning is enabled:

  • All Windows versions later than Windows 2003
  • Windows 2003 and earlier versions if the boot.ini file contains the /3GB switch

1.7 GB for Windows 2003 and earlier versions if the boot.ini file does not contain the /3GB switch

Table-level parameter limits

Table 2. Table-level parameter limits
Table-level parameters (2K page size unless otherwise stated) Maximum capacity per table
Data rows per page 255
Data rows per fragment 4,277,659,295
Data pages per fragment 16,775,134
Data bytes per fragment (excludes smart large objects (BLOB, CLOB) and simple large objects (BYTE, TEXT) created in blobspaces

2K page size = 33,818,670,144
4K page size =  68,174,144,576
8K page size =  136,885,093,440
12K page size =  205,596,042,304
16K page size =  274,306,991,168

Binary large object BLOB/CLOB pages 4 TB
Binary large objects TEXT/BYTE bytes 4 TB
Row length 32,767
Number of columns 32K
Maximum number of pages per index fragment 2,147,483,647
Key parts per index 16
Columns per functional index 102 (for C UDRs) 341 (for SPL or Java™ UDRs)
Maximum bytes per index key:

2K page size =    387
4K page size =    796
8K page size =  1615
12K page size =  2435
16K page size =  3254

Maximum size of an SQL statement Limited only by available memory

Informix System Defaults

Table 3. System defaults
Database characteristic Informix system default
Table lock mode Page
Initial extent size 8 pages
Next extent size 8 pages
Read-only isolation level (with database transactions) Committed Read
Read-only isolation level (ANSI-compliant database) Repeatable Read

Access capabilities

Table 4. Access capabilities
Access Capabilities Maximum Capacity per System
Maximum databases per Informix system 21 million
Maximum tables per Informix system 477 102 080
Maximum active users per Informix (minus the minimum number of system threads) 32K user threads
Maximum active users per database and table (also limited by the number of available locks, a tunable parameter) 32K user threads
Maximum number of open databases in a session UNIX: 32 databases

Windows: 8 databases

Maximum number of open tables per Informix system Dynamic allocation
Maximum number of open tables per user and join Dynamic allocation
Maximum number of open transactions per instance 32 767
Maximum locks per Informix system and database Dynamic allocation
Maximum number of page cleaners 128
Maximum number of partitions per dbspace 4K page size: 1048445, 2K page size: 1048314 (based on 4-bit bitmaps)
Maximum number of recursive synonym mappings 16
Maximum number of tables locked with LOCK TABLE per user 32
Maximum number of cursors per user Machine specific
Maximum Enterprise Replication transaction size 4 TB
Maximum dbspace size 131 PB
Maximum sbspace size 131 PB
Maximum chunk size 4 TB
Maximum number of chunks 32 766
Maximum number of 2K pages per chunk 2 billion
Maximum number of open Simple Large Objects (applies only to TEXT and BYTE data types) 20
Maximum number of B-tree levels 20
Maximum amount of decision support memory Machine specific
Utility support for large files 17 billion GB
Maximum number of storage spaces (dbspaces, blobspaces, sbspaces, or extspaces) 2047

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