Miscellaneous limits

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There are some other IBM® i system limits, such as the number of basic disk pools, the size of a user space, and the size of a message queue.

Table 1. Miscellaneous limits
Miscellaneous limits Value
Maximum system and I/O hardware configurations and capacities
Minimum load source size
  • DS8000® or virtual disks with VIOS as server: 35 GB for 520-byte sectors
  • SAN Volume Controller (SVC), Storwize®, virtual disks with VIOS VSCSI or IBM i as server: 40 GB (to get 35 GB usable space)
  • Native attached SAS/SCSI (both 520 byte or 4160 byte sectors): 70 GB
  • NVM Express (NVMe): 35 GB
Maximum load source size
  • 4096/4160 block disk: 16 TB minus 1 block
  • 512/520 block disk: 2 TB minus 1 block
Maximum disk size
  • 4096/4160 block disk: 16 TB minus 1 block
  • 512/520 block disk: 2 TB minus 1 block
Maximum number of disk arms that are contained in all of the basic auxiliary storage pools (ASPs 1 - 32), per partition 3 999
Maximum number of disk arms that are contained in all of the independent auxiliary storage pools (iASPs 33 - 255) in all nodes in a cluster 5 999
Minimum number of disk arms that are required for acceptable performance. See IBM Systems Workload Estimator.
Maximum number of active connections to a logical unit or disk unit in an external storage server or Virtual I/O Server environment. 8
Maximum combined number of disk arms and redundant connections to all disk units 35 600
Start of changeMaximum number of disk paths for VIOS attached 512-byte sector6 storage using Virtual Fibre Channel (VFC/NPIV)End of change Start of change35 600End of change
Start of changeMaximum number of disk paths for VIOS attached storage using Virtual SCSI (VSCSI)End of change Start of change35 600End of change
Maximum number of basic user ASPs 31
Maximum number of independent ASPs 223
Maximum number of logical partitions See Logical partitions.
Maximum database size for Domino® 64 GB
Maximum size of a user space 1 16 773 120 bytes
Maximum size of a user index 2 1 TB
Maximum size of a data queue or a user queue 3 2 GB
Maximum size of a message queue 4 16 MB (approximately 75 000 messages)
Maximum number of new messages of any one message type on a message queue Limited only by size of message queue
Maximum number of program messages that can be created in a job 5 4 294 967 293
Maximum number of records for each version of the history log 10 000 000
Maximum number of unique Volume IDs displayed/printed in Product Activity Log's Removable Media Lifetime Statistics for each Media Option 5000
Maximum number of input fields that can be specified for a display file 256
Maximum total size of concurrently used teraspace address ranges per job Approximately 64 TB
Range of user-defined double-byte characters that can be defined and maintained using the character generator utility (CGU) for Japanese Hexadecimal 6941 through 7FFE
Maximum memory per partition 32 TB
Minimum memory per partition Start of change4 GBEnd of change
Maximum number of processors per partition
  • POWER9 and POWER9 compatibility mode: 48 SMT8 processor cores. Can be expanded to 192 SMT8 processor cores with IBM Lab Services arrangement.
  • Start of changePower10 and Power10 compatibility mode: 48 SMT8 processor cores. Can be expanded to 240 SMT8 processor cores with IBM Lab Services arrangement.End of change
Maximum number of hardware threads per partition
  • POWER9 and POWER9 compatibility mode: 1 536
  • Start of changePower10 and Power10 compatibility mode: 1 920End of change
Maximum partition ID 1000
Maximum number of virtual SCSI optical devices per virtual SCSI adapter 16
Maximum number of virtual SCSI tape devices per virtual SCSI adapter 4
Maximum number of virtual SCSI disk devices per virtual SCSI adapter 32
Start of changeMaximum active disk paths per virtual Fibre Channel connection (NPIV)7End of change Start of change127 (Maximum 254 total active and passive paths combined)End of change
Start of changeMaximum active disk paths per physical Fibre Channel port (IBM i Native) - 16Gb or faster adapters7End of change Start of change127 (Maximum 254 total active and passive paths combined)End of change
Start of changeMaximum active disk paths per physical Fibre Channel port (IBM i Native) - 8Gb adapters7End of change Start of change64 (Maximum 128 total active and passive paths combined)End of change
Maximum Virtual I/O Server configurations and capacities See Specifications, Limitations, and Restrictions topics under "Planning for the Virtual I/O Server" in the documentation for your system.
Maximum number of workload capping groups 255
Maximum number of IMGCLG entries in a single IMGCLG 256
Maximum size of a virtual media 1 000 000 MB
Maximum number of virtual tape resources 35
Maximum number of virtual optical resources 35
Maximum number of active (varied on) optical devices 100
Maximum number of drives from a logical tape library can be attached to an IBM i partition 32
Maximum number of drives can be configured in a logical tape library attached to an IBM i partition 256
Maximum number of storage elements in one logical tape library 15 000
Maximum number of data blocks in a single file on tape 4 294 967 295
Start of changeMaximum number of tape LUNs (tape devices and control paths) per virtual Fibre Channel connection (NPIV)End of change Start of change127End of change
Start of changeMaximum number of tape LUNs (tape devices and control paths) per physical Fibre Channel adapter (IBM i Native)End of change Start of change127End of change
Start of changeMaximum number of paths to a multipath capable tape driveEnd of change Start of change8End of change
Notes:
  1. Listed size is the maximum when the machine is allowed to choose the alignment. Absolute maximum size of a user space is 16 776 704 bytes.
  2. To create a 1 TB capable user index when using the QUSCRTUI API, specify a value of 1 for the index size option. Otherwise, the size limit is 4 GB.
  3. The maximum size of a data queue that can be created through the data queue host server is 16 megabytes.
  4. Message queue QSYSOPR is shipped with a message queue full action of *WRAP. When the message queue is full, the oldest informational and answered messages are removed from the message queue to allow space for new messages to be added. If the removing of the informational and answered messages does not provide enough space, then unanswered inquiry messages are removed until there is space to add the new message. The default reply is sent before an unanswered inquiry message is removed. For more information, see the MSGQFULL parameter on the CHGMSGQ command.
  5. If the job has multiple threads, then the limit is the number of messages from all threads combined.
  6. Start of change512-byte sector disk resource types include 2145 (IBM SVC or Storwize Family) and D910 (EMC).End of change
  7. Start of changeThe documented limit assumes a standard configuration with up to one passive path for each active path. Certain advanced configurations such as HyperSwap will introduce the use of additional passive paths. When these advanced configurations are implemented, the maximum number of active paths per port is reduced. The overall combined path (active and passive) maximum per port is twice the active path limit documented here.End of change
Table 2. Interprocess Communication (IPC) limits
Interprocess Communication (IPC) limits Value
Maximum number of Single UNIX Specification message queues on the system 2 147 483 646
Maximum size of a Single UNIX Specification message queue 16 773 120 bytes
Maximum size of a single message on a Single UNIX Specification message queue 65 535 bytes
Maximum number of semaphore sets on the system 2 147 483 646
Maximum number of semaphores per semaphore set 65 535
Maximum number of shared memory segments that can be created on the system 2 147 483 646
Maximum size of a teraspace shared-memory segment that is created by using the shmget() function 4 294 967 295 bytes
Maximum size of a teraspace shared-memory segment that is created by using the shmget64() function 17 450 452 123 648 bytes
Maximum size of a resizeable teraspace shared-memory segment 268 435 456 bytes
Maximum size of a nonteraspace shared-memory segment 16 776 960 bytes
Maximum size of a resizeable nonteraspace shared-memory segment 16 773 120 bytes