Miscellaneous limits

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 Start of changeSee Start of changePower Systems Technical GuideEnd of change.End of change
Start of changeMinimum load source size End of change Start of change70 GBEnd of change
Start of changeMaximum load source sizeEnd of change Start of change
  • 512/520 block disk: 2 TB minus 1 block
  • 4096 block disk: 2 TB minus 1 block
  • 4160 block disk: 4 TB minus 1 block
End of change
Start of changeMaximum number of disk arms that are contained in all of the basic auxiliary storage pools (ASPs 1 - 32), per partitionEnd of change Start of change2 047End of change
Start of changeMaximum number of disk arms that are contained in all of the independent auxiliary storage pools (iASPs 33 - 255) in all nodes in a clusterEnd of change Start of change2 047End of change
Minimum number of disk arms that are required for acceptable performance. Start of changeSee Performance Papers and Articles in the Resource Library on the Start of change Performance ManagementEnd of change Link outside the Information Center website.End of change
Start of changeMaximum number of connections to a logical unit or disk unit in an external storage server or Virtual I/O Server environment.End of change 8
Maximum combined number of disk arms and redundant connections to a disk units 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 in the information center.
Maximum database size for Domino® 64 GB
Start of changeMaximum size of a user space 1End of change 16 773 120 bytes
Start of changeMaximum size of a user index 2End of change 1 TB
Start of changeMaximum size of a data queue or a user queue 3End of change 2 GB
Start of changeMaximum size of a message queue 4End of change 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
Start of changeMaximum number of program messages that can be created in a job 5End of change 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 Start of change16 TBEnd of change
Minimum memory per partition 256 MB
Maximum number of processors per partition 32 processor cores on Power7 systems and earlier running with a maximum of SMT4. Can be expanded to 96 processor cores with IBM Lab Services arrangement.
Maximum partition ID 1000
Start of changeStart of changeMaximum number of LUNs or optical devices that are associated with a virtual SCSI adapter pair for IBM iEnd of changeEnd of change Start of changeStart of change32End of changeEnd of change
Start of changeMaximum number of virtual target SCSI devices per virtual SCSI connectionEnd of change Start of change32End of change
Start of changeMaximum number of storage volumes per virtual fiber channel connection (NPIV)End of change Start of change64End of change
Start of changeMaximum Virtual I/O Server configurations and capacitiesEnd of change Start of changeSee Specifications, Limitations, and Restrictions topics under "Planning for the Virtual I/O Server" in the IBM Power Systems Hardware Information Center.End of change
Start of changeMaximum number of workload capping groupsEnd of change Start of change255End of change
Start of changeMaximum number of IMGCLG entries in a single IMGCLGEnd of change Start of change256End of change
Start of changeMaximum size of a virtual mediaEnd of change Start of change1 000 000 MBEnd of change
Start of changeMaximum number of virtual tape resourcesEnd of change Start of change35End of change
Start of changeMaximum number of virtual optical resourcesEnd of change Start of change35End of change
Start of changeMaximum number of active (varied on) optical devicesEnd of change Start of change100End of change
Start of changeMaximum number of drives from a logical tape library can be attached to an IBM i partitionEnd of change Start of change32End of change
Start of changeMaximum number of drives can be configured in a logical tape library attached to an IBM i partitionEnd of change Start of change256End of change
Start of changeMaximum number of storage elements in one logical tape libraryEnd of change Start of change15 000End of change
Start 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. Start of changeTo 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.End of change
  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.
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
Start of changeMaximum size of a teraspace shared-memory segment that is created by using the shmget() functionEnd of change 4 294 967 295 bytes
Start of changeMaximum size of a teraspace shared-memory segment that is created by using the shmget64() functionEnd of change 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