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
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 (LARGE tables and 2K page size unless otherwise stated) Maximum capacity per table
Data rows per page 29,122 with 256k page size
Data rows per fragment 9.2 quintillion
Data pages per fragment 140.7 trillion
Data bytes per fragment (excludes smart large objects (BLOB, CLOB) and simple large objects (BYTE, TEXT) created in blobspaces

2K page size = 256 PB
8K page size =  1 EB
16K page size =  2 EB
32K page size = 4 EB
64K page size = 8 EB
128K page size = 16 EB
256K page size = 32 EB
Binary large object BLOB/CLOB pages 4 EB per smartblob space
Binary large objects TEXT/BYTE bytes 16 ZB per blobspace
Row length 32,767
Number of columns 32K
Maximum number of pages per index fragment 9.2 quintillion
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 =    380
4K page size =    790
8K page size =  1,609
16K page size =  3,247
32K page size = 6,520
64K page size = 13,074
128K page size = 26,181
256K page size = 32,267
Maximum size of an SQL statement Limited only by available memory

Informix® System Defaults

Table 3. System defaults

Each row in the following table lists a database characteristic followed by the Informix® system default for that characteristic.

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 500 ZB
Maximum sbspace size 8 EB
Maximum chunk size 8 EB
Maximum number of chunks 65,534
Maximum number of 2K pages per chunk 4.5 quadrillion
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