diff --git a/include_core/unix/thrdsup.h b/include_core/unix/thrdsup.h
index 7ec1bb57463..3f68ea04755 100644
--- a/include_core/unix/thrdsup.h
+++ b/include_core/unix/thrdsup.h
@@ -89,6 +89,10 @@ int linux_pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex, c
 intptr_t init_thread_library(void);
 intptr_t set_pthread_priority(pthread_t handle, omrthread_prio_t j9ThreadPriority);
 intptr_t set_pthread_name(pthread_t self, pthread_t thread, const char *name);
+intptr_t sem_init_zos(j9sem_t s, int pShared, int initValue);
+intptr_t sem_destroy_zos(j9sem_t s);
+intptr_t sem_wait_zos(j9sem_t s);
+intptr_t sem_post_zos(j9sem_t s);
 
 extern struct J9ThreadLibrary default_library;
 
diff --git a/port/zos390/omrcel4ro31.h b/port/zos390/omrcel4ro31.h
index 516f4153ffd..fe04f978387 100644
--- a/port/zos390/omrcel4ro31.h
+++ b/port/zos390/omrcel4ro31.h
@@ -124,7 +124,7 @@ omr_cel4ro31_call(OMR_CEL4RO31_infoBlock *infoBlock);
  * @return whether CEL4RO31 runtime support is available.
  */
 BOOLEAN
-omr_cel4ro31_isSupported(void);
+omr_cel4ro31_is_supported(void);
 
 /**
  * A helper routine to return an error message associated with the CEL4RO31 return code.
diff --git a/port/zos390/omrgetjobid.c b/port/zos390/omrgetjobid.c
index c2a88925724..a2e08b498c8 100644
--- a/port/zos390/omrgetjobid.c
+++ b/port/zos390/omrgetjobid.c
@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include "omrport.h"
 #include "omrgetjobid.h"
+#include "omrportpriv.h"
 
 #define JOBID_STRING_LENGTH 9
 
diff --git a/port/zos390/omrgetjobname.c b/port/zos390/omrgetjobname.c
index 5131f41df35..ce1f3b0b26c 100644
--- a/port/zos390/omrgetjobname.c
+++ b/port/zos390/omrgetjobname.c
@@ -48,6 +48,7 @@ void
 omrget_jobname(struct OMRPortLibrary *portLibrary, char *jobname, uintptr_t length)
 {
 	char *tmp_jobname = (char *)__malloc31(J9_MAX_JOBNAME);
+	extern void _JOBNAME(char *); /* defined in omrjobname.s */
 
 	if (NULL != tmp_jobname) {
 		char *ascname = NULL;
diff --git a/port/zos390/omrgetsysname.c b/port/zos390/omrgetsysname.c
index 8040d329177..a19ba427570 100644
--- a/port/zos390/omrgetsysname.c
+++ b/port/zos390/omrgetsysname.c
@@ -21,6 +21,7 @@
  *******************************************************************************/
 
 #include <stdlib.h>
+#include <string.h>
 #include <sys/utsname.h>
 #include "omrgetsysname.h"
 
diff --git a/port/zos390/omrgetuserid.c b/port/zos390/omrgetuserid.c
index e17bde4caf6..45908850b78 100644
--- a/port/zos390/omrgetuserid.c
+++ b/port/zos390/omrgetuserid.c
@@ -54,6 +54,7 @@ omrget_userid(char *userid, uintptr_t length)
 	uintptr_t result = 0;
 
 	userid[0] = '\0';
+	extern void _USERID(char *); /* defined in omruserid.s */
 
 	if (NULL != tmp_userid) {
 		char *ascname = NULL;
diff --git a/port/zos390/omrintrospect.h b/port/zos390/omrintrospect.h
index 6915cb916f7..60473f4d9a3 100644
--- a/port/zos390/omrintrospect.h
+++ b/port/zos390/omrintrospect.h
@@ -34,22 +34,25 @@
 #include "omrintrospect_common.h"
 #include "omrutil.h"
 
-#pragma linkage(getthent, OS_UPSTACK)
 #if defined(OMR_ENV_DATA64)
+#pragma linkage(getthent, OS)
 #pragma map(getthent, "BPX4GTH")
-#else
+#else /* defined(OMR_ENV_DATA64) */
+#pragma linkage(getthent, OS_UPSTACK)
 #pragma map(getthent, "BPX1GTH")
-#endif
+#endif /* defined(OMR_ENV_DATA64) */
 
-#pragma linkage(pthread_quiesce, OS_UPSTACK)
 #if defined(OMR_ENV_DATA64)
 #pragma map(pthread_quiesce, "BPX4PTQ")
-#else
+#else /* defined(OMR_ENV_DATA64) */
+#pragma linkage(pthread_quiesce, OS_UPSTACK)
 #pragma map(pthread_quiesce, "BPX1PTQ")
-#endif
+#endif /* defined(OMR_ENV_DATA64) */
 
+#if !defined(OMR_ENV_DATA64)
 #pragma linkage(pthread_quiesce_and_get_np_X, OS_UPSTACK)
 #pragma map(pthread_quiesce_and_get_np_X, "BPX1PQG")
+#endif /*  !defined(OMR_ENV_DATA64) */
 
 #ifdef MAX_NAME
 #undef MAX_NAME
@@ -60,8 +63,11 @@
 
 typedef __mcontext_t_ thread_context;
 
-
+#if defined(__open_xl__)
+#pragma pack(push, 1)
+#else /* defined(__open_xl__) */
 #pragma pack(packed)
+#endif /* defined(__open_xl__) */
 
 /* Program routine entry area (XPLINK) */
 typedef struct XPLINK_Routine_entry {
@@ -633,6 +639,10 @@ struct tcb {
 #define QUIESCE_SRB          9  /*  Quiesce threads type = SRBs      @DGA */
 /* Skip 10 and 11 due to collision with BPXZCONS Freeze/Unfreeze Fast */
 
+#if defined(__open_xl__)
+#pragma pack(pop)
+#else /* defined(__open_xl__) */
 #pragma pack(reset)
+#endif /* defined(__open_xl__) */
 
 #endif
diff --git a/port/zos390/omrosbacktrace_impl.c b/port/zos390/omrosbacktrace_impl.c
index 82c89acd7c7..859d80e135b 100644
--- a/port/zos390/omrosbacktrace_impl.c
+++ b/port/zos390/omrosbacktrace_impl.c
@@ -27,6 +27,7 @@
  */
 
 #include "omrport.h"
+#include "omrportpriv.h"
 #include "omrsignal_context.h"
 #include <stdio.h>
 #include <signal.h>
diff --git a/port/zos390/omrosdump.c b/port/zos390/omrosdump.c
index 4f98a4fdf89..8325fa92c02 100644
--- a/port/zos390/omrosdump.c
+++ b/port/zos390/omrosdump.c
@@ -26,6 +26,7 @@
  * @brief Dump formatting
  */
 
+#define _EXT
 
 #include <errno.h>
 #include <stdio.h>
@@ -37,7 +38,9 @@
 #include <time.h>
 #include <pwd.h>
 #include <ctest.h>
+#include "omrgetjobname.h"
 #include "omrport.h"
+#include "omrportpriv.h"
 #if defined(J9ZOS390) && !defined(OMR_EBCDIC)
 #include "atoe.h"
 #endif
@@ -333,6 +336,8 @@ tdump(struct OMRPortLibrary *portLibrary, char *asciiLabel, char *ebcdicLabel, u
 		char dsn[256];
 	} *dsnPattern31;
 
+	extern void _TDUMP(struct ioparms_t *ioparms, struct dsn_pattern_t *dsn_pattern); /* defined in omrgenerate_ieat_dump.s */
+
 	/* _TDUMP subroutine expects 31 bit addresses */
 	ioParms31 = __malloc31(sizeof(*ioParms31));
 	if (ioParms31 == NULL) {
diff --git a/port/zos390/omrsignal_context.c b/port/zos390/omrsignal_context.c
index e38c3a0af4b..3f2d4eb42a9 100644
--- a/port/zos390/omrsignal_context.c
+++ b/port/zos390/omrsignal_context.c
@@ -22,6 +22,7 @@
 
 #include "omrport.h"
 #include "omrportpriv.h"
+#include <strings.h>
 #include <unistd.h>
 #include "omrsignal_context.h"
 #include "omrceeocb.h"
diff --git a/port/zos390/omrsignal_context.h b/port/zos390/omrsignal_context.h
index f0a3545e010..13a8d1280e1 100644
--- a/port/zos390/omrsignal_context.h
+++ b/port/zos390/omrsignal_context.h
@@ -57,6 +57,7 @@ uint32_t infoForVR(struct OMRPortLibrary *portLibrary, OMRUnixSignalInfo *info,
 uint32_t infoForModule(struct OMRPortLibrary *portLibrary, struct OMRUnixSignalInfo *info, int32_t index, const char **name, void **value);
 uint32_t infoForControl(struct OMRPortLibrary *portLibrary, struct OMRUnixSignalInfo *info, int32_t index, const char **name, void **value);
 uint32_t infoForSignal(struct OMRPortLibrary *portLibrary, struct OMRUnixSignalInfo *info, int32_t index, const char **name, void **value);
+void fillInJumpInfo(struct OMRPortLibrary *portLibrary, void *contextInfo, void *jumpInfo);
 void fillInUnixSignalInfo(struct OMRPortLibrary *portLibrary, void *contextInfo, struct OMRUnixSignalInfo *signalInfo);
 BOOLEAN checkIfResumableTrapsSupported(struct OMRPortLibrary *portLibrary);
 
diff --git a/thread/unix/thrdsup.c b/thread/unix/thrdsup.c
index c3c3ebecbbb..b87ee789d52 100644
--- a/thread/unix/thrdsup.c
+++ b/thread/unix/thrdsup.c
@@ -66,12 +66,10 @@ intptr_t init_thread_library(void);
 static intptr_t zos_init_yielding(void);
 #endif
 intptr_t sem_getvalue_zos(j9sem_t s);
-intptr_t sem_init_zos(j9sem_t s, int pShared, int initValue);
 void call_omrthread_init(void);
-intptr_t sem_destroy_zos(j9sem_t s);
-intptr_t sem_wait_zos(j9sem_t s);
 intptr_t sem_trywait_zos(j9sem_t s);
-intptr_t sem_post_zos(j9sem_t s);
+int setenv(const char *, const char *, int) __THROW;
+char *getenv(const char *) __THROW;
 
 #if defined (OMRZTPF)
 void  ztpf_init_proc(void);
diff --git a/util/omrutil/unix/zos/getstoragekey.c b/util/omrutil/unix/zos/getstoragekey.c
index d330657ee38..5502b785ece 100644
--- a/util/omrutil/unix/zos/getstoragekey.c
+++ b/util/omrutil/unix/zos/getstoragekey.c
@@ -26,6 +26,7 @@
 uintptr_t
 getStorageKey(void)
 {
+	extern uintptr_t _GETPSW(); /* defined in getpsw.s */
 	/* The storage key is returned in bits 8-11 of the PSW */
 	return ((_GETPSW() >> 20) & 0xF);
 }