Purpose
Chooses the mode used by TDP to send I/O to the database.
Syntax
where:
- EXCP
- CP I/O be performed using EXCP
- EXCPVR
- CP I/O be performed using EXCPVR.
- IOSDRIVR
- CP I/O be performed using a TDP IOS Driver.
Usage Notes
If no CPs are started, IOMODE is validated but ignored.
Use of IOSDRIVR reduces the I/O path length between TDP I/O tasks and the system I/O supervisor. Use of the option also avoids Supervisor Call (SVC) interrupts by enabling TDP to pass any new I/O request directly to the IOS.
For z/OS, use of EXCPVR or IOSDRIVR, allows 31bit virtual storage for I/O buffers.
For z/OS, use of EXCPVR or IOSDRIVR results in virtual storage for I/O being fixed in real storage while it is allocated, so real storage utilization can be increased. For CCU-type CPs, such storage is dynamically obtained, freed, or cached as needed; for CIC-type CPs, the storage comprises TDP I/O cells.
Example 1: INITIAL IOMODE
INIT IOMODE EXCP
Example 2: INITIAL IOMODE
INITIAL IOMODE EXCPVR
Example 3: INITIAL IOMODE
INIT IOMODE IOSDRIVR