Steps for diagnosing a disabled loop

In an IPCS session, enter the IPCS STATUS CPU command to examine status of each CP. For example:

CPU(X'02') STATUS: 
PSW=04042000 80000000 00000000 011E8592 
(Running in PRIMARY, key 0, AMODE 31, DAT ON) 
Disabled for PER I/O EXT 
NOCPU ASID(X'0001') 011E8592. IEANUC01.IEAVELKX+073A IN READ ONLY NUCLEUS 
ASCB1 at FD3400, JOB(*MASTER*), for the home ASID 
ASXB1 at FD3598 and a local SRB for the home ASID 
HOME ASID: 0001 PRIMARY ASID: 0001 SECONDARY ASID: 0001 


CLTE: 01F76020 
+0000 BLSD..... 00000000 XDS...... 00000000 XRES..... 00000000 XQ....... 00FD3018 ESET..... 00FD3028 IXSC..... 00000000
+0018 IXSH..... 00FD3040 IXDS..... 00000000 IXLL..... 00000000 ULUT..... 00FD3030 IXRE..... 00000000 WLMR..... 00000000
+0030 WLMQ..... 00FD3050 REGS..... 00000000 CNTX..... 00FD3060 SSD...... 00000000 
HOLDING LOCK(S): CPU 
CURRENT FRR STACK IS: NORMAL

In the preceding example, the PSW for CP 2 indicates that it is executing disabled in CSECT IEAVELKX, the lock manager. The status for CP 4 indicates several locks are held, therefore, this is a normal spin in IEAVELKX. The loop that is causing the problem is in IAXRC.

CPU(X'04') STATUS: 
PSW=04040000 80000000 00000000 017D5126 
(Running in PRIMARY, key 0, AMODE 31, DAT ON) 
Disabled for PER I/O EXT 
NOCPU ASID(X'0001') 017D5126. IEANUC01.IAXRC+034E IN READ ONLY NUCLEUS 
ASCB1 at FD3400, JOB(*MASTER*), for the home ASID 
ASXB1 at FD3598 for the home ASID. No block is dispatched 
HOME ASID: 0001 PRIMARY ASID: 0003 SECONDARY ASID: 0367 

CLTE: 01B19000 
+0000 BLSD..... 00000000 XDS...... 00000000 XRES..... 00000000 XQ....... 00FD3018 ESET..... 00FD3028 IXSC..... 00000000
+0018 IXSH..... 00FD3040 IXDS..... 00000000 IXLL..... 00000000 ULUT..... 00FD3030 IXRE..... 00000000 WLMR..... 00000000
+0030 WLMQ..... 00FD3050 REGS..... 00000000 CNTX..... 00FD3060 SSD...... 00000000 
HOLDING LOCK(S): CPU RSM RSMCM RSMST RSMAD 
CURRENT FRR STACK IS: NORMAL

Use the name of the CSECT executing on CP 4, IARXC and the symptom LOOP to check for a known problem. From the module prefix, identify the component, subsystem, or product, if provided by IBM.
Use the module name to query the SMP/E zone for a module entry with that module name. If the search does not find a match, the module is not an IBM module. If the search indicates a match, use the FMID to positively identify the product.
Continue diagnosis as follows:
1. If all the addresses are in components of z/OS, continue with Searching the problem reporting databases.
2. If all the addresses are in an IBM subsystem or product, continue diagnosis with the diagnosis publication for the subsystem or product. See Diagnosis information for z/OS base elements and features for the correct publication.
3. If all the addresses are in components of z/OS and in an IBM subsystem or product, continue with Searching the problem reporting databases and with the diagnosis book for the subsystem or product. See Diagnosis information for z/OS base elements and features for the correct publication.
4. If any of the addresses are in an installation-provided program, including an installation exit routine, continue diagnosis with that program, using the dump.
5. If some addresses are in the program or routine and some in system modules, the loop is probably in the program or routine and includes one or more requests for system services.