NSUBTKS parameter
Max number of pseudo-subtasks
Summary
- Default value
- 4
- Parameter type
- System
- Where set
- On User 0's parameter line
- Related products
- All
- Introduced
- Model 204 V2.1 or earlier
Description
The maximum number of pseudo subtasks that can be generated by Model 204 during a run.
Pseudo subtasks are internal processes that perform special functions such as automatic checkpointing and controlling input and output operations for SNA Communications Server terminals.
The algorithm to determine if NSERVS, NUSERS, and NSUBTKS are too large is:
IF NUSERS=NSERVS NUSERS + NSUBTKS + 1 > 32767 ELSE NSERVS + NUSERS + NSUBTKS + 1 > 32767
If too many process control blocks have been requested, the user receives the following message:
M204.0021: NSERVS+NUSERS(IF SWAPPING)+NSUBTKS+1 > 32767
Each server, user, pseudo subtask, and the Scheduler has a process control block. There may not be more than 32767 process control blocks.
If you receive the M204.0021 message, adjust the combination of NUSERS, NSERVS, and NSUBTKS + 1 so that it does not exceed 32767.
The Model 204 services that call pseudo subtasks are listed in the table below along with the number of pseudo subtasks that each uses. Set NSUBTKS to at least the sum of the pseudo subtasks called for by your configuration of Model 204.
| Service | Pseudo subtasks |
|---|---|
| SNA Communications Server 3270 interface (z/OS, z/VSE) | 3 for IODEV=7 |
| SNA Communications Server 3767/NTO interface | 3 for IODEV=37
Note: The IODEV=37 setting is no longer supported as of Model 204 version 7.7. |
| CMS/SNA Communications Server interface | 3 for IODEV=7
2 for each SNA Communications Server terminal ACB |
| Horizon or Parallel Query Option/204 | 2 for each open link (z/OS)
4 for each open link (z/VM) |
| Connect★ | 2 for each open Horizon for VTAM link (4, if under z/VM)
1 for each open CRAM or IUCV SQL link 3 for first open Horizon for TCP/IP link; 2 for each subsequent link |
| Performance statistics | 1 for printing partial statistics
1 for logging to audit trail |
| Checkpointing | 1 for RCVOPT '1' bit on
1 for nonzero CPTIME setting 1 for nonzero setting of CPTO, CPTQ, or both 1 for the CHKPAWW pseudo subtask (XA and ESA environments only) |
| CMS external security | 1 for a security service machine |
| LIOS | 1 for each LIOS ring stream |