diff --git a/all.sas b/all.sas
index 921f8ea..83f0aea 100644
--- a/all.sas
+++ b/all.sas
@@ -2337,9 +2337,9 @@ Usage:
 %mend mp_appendfile;/**
   @file
   @brief Apply a set of formats to a table
-  @details Applies a set of formats to one or more SAS datasets.  Can be used
-    to migrate formats from one table to another.  The input table must contain
-    the following columns:
+  @details Applies a set of formats to the metadata of one or more SAS datasets.
+    Can be used to migrate formats from one table to another.  The input table
+    must contain the following columns:
 
     @li lib - the libref of the table to be updated
     @li ds - the dataset to be updated
@@ -7575,19 +7575,29 @@ select distinct lowcase(memname)
   Only useful if every update uses the macro!   Used heavily within
   [Data Controller for SAS](https://datacontroller.io).
 
-  The underlying table is structured as per the MAKETABLE action.
-
   @param [in] action The action to be performed.  Valid values:
     @li LOCK - Sets the lock flag, also confirms if a SAS lock is available
     @li UNLOCK - Unlocks the table
-    @li MAKETABLE - creates the control table (ctl_ds)
   @param [in] lib= (WORK) The libref of the table to lock.  Should already be
     assigned.
   @param [in] ds= The dataset to lock
   @param [in] ref= A meaningful reference to enable the lock to be traced. Max
     length is 200 characters.
   @param [out] ctl_ds= (0) The control table which controls the actual locking.
-    Should already be assigned and available.
+    Should already be assigned and available.  Definition as follows:
+
+        proc sql;
+        create table &ctl_ds(
+            lock_lib char(8),
+            lock_ds char(32),
+            lock_status_cd char(10) not null,
+            lock_user_nm char(100) not null ,
+            lock_ref char(200),
+            lock_pid char(10),
+            lock_start_dttm num format=E8601DT26.6,
+            lock_end_dttm num format=E8601DT26.6,
+          constraint pk_mp_lockanytable primary key(lock_lib,lock_ds));
+
   @param [in] loops= (25) Number of times to check for a lock.
   @param [in] loop_secs= (1) Seconds to wait between each lock attempt
 
@@ -7791,19 +7801,6 @@ run;
     %let abortme=1;
   %end;
 %end;
-%else %if &action=MAKETABLE %then %do;
-  proc sql;
-  create table &ctl_ds(
-      lock_lib char(8),
-      lock_ds char(32),
-      lock_status_cd char(10) not null,
-      lock_user_nm char(100) not null ,
-      lock_ref char(200),
-      lock_pid char(10),
-      lock_start_dttm num format=E8601DT26.6,
-      lock_end_dttm num format=E8601DT26.6,
-    constraint pk_mp_lockanytable primary key(lock_lib,lock_ds));
-%end;
 %else %do;
   %let msg=lock_anytable given unsupported action (&action);
   %let abortme=1;
@@ -8304,6 +8301,254 @@ data _null_;
 run;
 
 %mend mp_resetoption;/**
+  @file
+  @brief Generate and apply retained key values to a staging table
+  @details This macro will populate a staging table with a Retained Key based on
+  a business key and a base (target) table.
+
+  Definition of retained key ([source](
+    http://bukhantsov.org/2012/04/what-is-data-vault/)):
+
+  > The retained key is a key which is mapped to business key one-to-one. In
+  > comparison,  the surrogate key includes time and there can be many surrogate
+  > keys corresponding to one business key. This explains the name of the key,
+  > it is retained with insertion of a new version of a row while surrogate key
+  > is increasing.
+
+  This macro is designed to be used as part of a wider load / ETL process (such
+  as the one in [Data Controller for SAS](https://datacontroller.io)).
+
+  Specifically, the macro assumes that the base table has already been 'locked'
+  (eg with the mp_lockanytable.sas macro) prior to invocation.  Also, several
+  tables are assumed to exist (names are configurable):
+
+  @li work.staging_table - the staged data, minus the retained key element
+  @li permlib.base_table - the target table to be loaded (**not** loaded by this
+    macro)
+  @li permlib.maxkeytable - optional, used to store load metaadata.
+  The structure is as follows:
+
+      proc sql;
+      create table yourlib.maxkeytable(
+          keytable varchar(41) label='Base table in libref.dataset format',
+          keycolumn char(32) format=$32.
+            label='The Retained key field containing the key values.',
+          max_key num label=
+            'Integer representing current max RK or SK value in the KEYTABLE',
+          processed_dttm num format=E8601DT26.6
+            label='Datetime this value was last updated',
+        constraint pk_mpe_maxkeyvalues
+            primary key(keytable));
+
+  @param [in] base_lib= (WORK) Libref of the base (target) table.
+  @param [in] base_dsn= (BASETABLE) Name of the base (target) table.
+  @param [in] append_lib= (WORK) Libref of the staging table
+  @param [in] append_dsn= (APPENDTABLE) Name of the staging table
+  @param [in] retained_key= (DEFAULT_RK) Name of RK to generate (should exist on
+    base table)
+  @param [in] business_key= (PK1 PK2) Business key against which to generate
+    RK values.  Should be unique and not null on the staging table.
+  @param [in] check_uniqueness=(NO) Set to yes to perform a uniqueness check.
+    Recommended if there is a chance that the staging data is not unique on the
+    business key.
+  @param [in] maxkeytable= (0) Provide a maxkeytable libds reference here, to
+    store load metadata (maxkey val, load time).  Set to zero if metadata is not
+    required, eg, when preparing a 'dummy' load. Structure is described above.
+    See below for sample data.
+    |KEYTABLE:$32.|KEYCOLUMN:$32.|MAX_KEY:best.|PROCESSED_DTTM:E8601DT26.6|
+    |---|---|---|---|
+    |`DC487173.MPE_SELECTBOX `|`SELECTBOX_RK `|`55 `|`1950427787.8 `|
+    |`DC487173.MPE_FILTERANYTABLE `|`filter_rk `|`14 `|`1951053886.8 `|
+  @param [in] locktable= (0) If updating the maxkeytable, provide the libds
+    reference to the lock table (per mp_lockanytable.sas macro)
+  @param [in] filter_str= Apply a filter - useful for SCD2 or BITEMPORAL loads.
+    Example: `filter_str=%str( (where=( &now < &tech_to)) )`
+  @param [out] outds= (WORK.APPEND) Output table (staging table + retained key)
+
+  <h4> SAS Macros </h4>
+  @li mf_existvar.sas
+  @li mf_getquotedstr.sas
+  @li mf_getuniquename.sas
+  @li mf_nobs.sas
+  @li mp_abort.sas
+  @li mp_lockanytable.sas
+
+  <h4> Related Macros </h4>
+  @li mp_retainedkey.test.sas
+
+  @version 9.2
+
+**/
+
+%macro mp_retainedkey(
+  base_lib=WORK
+  ,base_dsn=BASETABLE
+  ,append_lib=WORK
+  ,append_dsn=APPENDTABLE
+  ,retained_key=DEFAULT_RK
+  ,business_key= PK1 PK2
+  ,check_uniqueness=NO
+  ,maxkeytable=0
+  ,locktable=0
+  ,outds=WORK.APPEND
+  ,filter_str=
+);
+%put &sysmacroname entry vars:;
+%put _local_;
+
+%local base_libds app_libds key_field check maxkey idx_pk newkey_cnt iserr
+  msg x tempds1 tempds2 comma_pk appnobs checknobs dropvar tempvar idx_val;
+%let base_libds=%upcase(&base_lib..&base_dsn);
+%let app_libds=%upcase(&append_lib..&append_dsn);
+%let tempds1=%mf_getuniquename();
+%let tempds2=%mf_getuniquename();
+%let comma_pk=%mf_getquotedstr(in_str=%str(&business_key),dlm=%str(,),quote=);
+
+/* validation checks */
+%let iserr=0;
+%if &syscc>0 %then %do;
+  %let iserr=1;
+  %let msg=%str(SYSCC=&syscc on macro entry);
+%end;
+%else %if %sysfunc(exist(&base_libds))=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Base LIBDS (&base_libds) expected but NOT FOUND);
+%end;
+%else %if %sysfunc(exist(&app_libds))=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Append LIBDS (&app_libds) expected but NOT FOUND);
+%end;
+%else %if &maxkeytable ne 0 and %sysfunc(exist(&maxkeytable))=0  %then %do;
+  %let iserr=1;
+  %let msg=%str(Maxkeytable (&maxkeytable) expected but NOT FOUND);
+%end;
+%else %if &maxkeytable ne 0 and %sysfunc(exist(&locktable))=0  %then %do;
+  %let iserr=1;
+  %let msg=%str(Locktable (&locktable) expected but NOT FOUND);
+%end;
+%else %if %length(&business_key)=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Business key (&business_key) expected but NOT FOUND);
+%end;
+
+%do x=1 %to %sysfunc(countw(&business_key));
+  /* check business key values exist */
+  %let key_field=%scan(&business_key,&x,%str( ));
+  %if (not %mf_existvar(&app_libds,&key_field))
+    or (not %mf_existvar(&base_libds,&key_field))
+  %then %do;
+    %let iserr=1;
+    %let msg=Business key (&key_field) not found!;
+  %end;
+%end;
+
+%if &iserr=1 %then %do;
+  /* err case so first perform an unlock of the base table before exiting */
+  %mp_lockanytable(
+    UNLOCK,lib=&base_lib,ds=&base_dsn,ref=%superq(msg),ctl_ds=&locktable
+  )
+%end;
+%mp_abort(iftrue=(&iserr=1),mac=mp_retainedkey,msg=%superq(msg))
+
+proc sql noprint;
+select sum(max(&retained_key),0) into: maxkey from &base_libds;
+
+/**
+  * get base table RK and bus field values for lookup
+  */
+proc sql noprint;
+create table &tempds1 as
+  select distinct &comma_pk,&retained_key
+  from &base_libds &filter_str
+  order by &comma_pk,&retained_key;
+
+%if &check_uniqueness=YES %then %do;
+  select count(*) into:checknobs
+    from (select distinct &comma_pk from &app_libds);
+  select count(*) into: appnobs from &app_libds; /* might be view */
+  %if &checknobs ne &appnobs %then %do;
+    %let msg=Source table &app_libds is not unique on (&business_key);
+    %let iserr=1;
+  %end;
+%end;
+%if &iserr=1 %then %do;
+  /* err case so first perform an unlock of the base table before exiting */
+  %mp_lockanytable(
+    UNLOCK,lib=&base_lib,ds=&base_dsn,ref=%superq(msg),ctl_ds=&locktable
+  )
+%end;
+%mp_abort(iftrue= (&iserr=1),mac=mp_retainedkey,msg=%superq(msg))
+
+%if %mf_existvar(&app_libds,&retained_key)
+%then %let dropvar=(drop=&retained_key);
+
+/* prepare interim table with retained key populated for matching keys */
+proc sql noprint;
+create table &tempds2 as
+  select b.&retained_key, a.*
+  from &app_libds &dropvar a
+  left join &tempds1 b
+  on 1
+  %do idx_pk=1 %to %sysfunc(countw(&business_key));
+    %let idx_val=%scan(&business_key,&idx_pk);
+    and a.&idx_val=b.&idx_val
+  %end;
+  order by &retained_key;
+
+/* identify the number of entries without retained keys (new records) */
+select count(*) into: newkey_cnt
+  from &tempds2
+  where missing(&retained_key);
+quit;
+
+/**
+  * Update maxkey table if link provided
+  */
+%if &maxkeytable ne 0 %then %do;
+  proc sql;
+  select count(*) into: check from &maxkeytable
+    where upcase(keytable)="&base_libds";
+
+  %mp_lockanytable(LOCK
+    ,lib=%scan(&maxkeytable,1,.)
+    ,ds=%scan(&maxkeytable,2,.)
+    ,ref=Updating maxkeyvalues with mp_retainedkey
+    ,ctl_ds=&locktable
+  )
+  proc sql;
+  %if &check=0 %then %do;
+  insert into &maxkeytable
+    set keytable="&base_libds"
+      ,keycolumn="&retained_key"
+      ,max_key=%eval(&maxkey+&newkey_cnt)
+      ,processed_dttm="%sysfunc(datetime(),E8601DT26.6)"dt;
+  %end;
+  %else %do;
+  update &maxkeytable
+    set max_key=%eval(&maxkey+&newkey_cnt)
+      ,processed_dttm="%sysfunc(datetime(),E8601DT26.6)"dt
+    where keytable="&base_libds";
+  %end;
+  %mp_lockanytable(UNLOCK
+    ,lib=%scan(&maxkeytable,1,.)
+    ,ds=%scan(&maxkeytable,2,.)
+    ,ref=Updating maxkeyvalues with maxkey=%eval(&maxkey+&newkey_cnt)
+    ,ctl_ds=&locktable
+  )
+%end;
+
+/* fill in the missing retained key values */
+%let tempvar=%mf_getuniquename();
+data &outds(drop=&tempvar);
+  retain &tempvar %eval(&maxkey+1);
+  set &tempds2;
+  if &retained_key =. then &retained_key=&tempvar;
+  &tempvar=&tempvar+1;
+run;
+
+%mend mp_retainedkey;
+
+/**
   @file mp_runddl.sas
   @brief An opinionated way to execute DDL files in SAS.
   @details When delivering projects there should be seperation between the DDL
diff --git a/base/mp_applyformats.sas b/base/mp_applyformats.sas
index 7bdb1a0..d6b4b83 100644
--- a/base/mp_applyformats.sas
+++ b/base/mp_applyformats.sas
@@ -1,9 +1,9 @@
 /**
   @file
   @brief Apply a set of formats to a table
-  @details Applies a set of formats to one or more SAS datasets.  Can be used
-    to migrate formats from one table to another.  The input table must contain
-    the following columns:
+  @details Applies a set of formats to the metadata of one or more SAS datasets.
+    Can be used to migrate formats from one table to another.  The input table
+    must contain the following columns:
 
     @li lib - the libref of the table to be updated
     @li ds - the dataset to be updated
diff --git a/base/mp_lockanytable.sas b/base/mp_lockanytable.sas
index d25be87..adabb6e 100644
--- a/base/mp_lockanytable.sas
+++ b/base/mp_lockanytable.sas
@@ -5,19 +5,29 @@
   Only useful if every update uses the macro!   Used heavily within
   [Data Controller for SAS](https://datacontroller.io).
 
-  The underlying table is structured as per the MAKETABLE action.
-
   @param [in] action The action to be performed.  Valid values:
     @li LOCK - Sets the lock flag, also confirms if a SAS lock is available
     @li UNLOCK - Unlocks the table
-    @li MAKETABLE - creates the control table (ctl_ds)
   @param [in] lib= (WORK) The libref of the table to lock.  Should already be
     assigned.
   @param [in] ds= The dataset to lock
   @param [in] ref= A meaningful reference to enable the lock to be traced. Max
     length is 200 characters.
   @param [out] ctl_ds= (0) The control table which controls the actual locking.
-    Should already be assigned and available.
+    Should already be assigned and available.  Definition as follows:
+
+        proc sql;
+        create table &ctl_ds(
+            lock_lib char(8),
+            lock_ds char(32),
+            lock_status_cd char(10) not null,
+            lock_user_nm char(100) not null ,
+            lock_ref char(200),
+            lock_pid char(10),
+            lock_start_dttm num format=E8601DT26.6,
+            lock_end_dttm num format=E8601DT26.6,
+          constraint pk_mp_lockanytable primary key(lock_lib,lock_ds));
+
   @param [in] loops= (25) Number of times to check for a lock.
   @param [in] loop_secs= (1) Seconds to wait between each lock attempt
 
@@ -221,19 +231,6 @@ run;
     %let abortme=1;
   %end;
 %end;
-%else %if &action=MAKETABLE %then %do;
-  proc sql;
-  create table &ctl_ds(
-      lock_lib char(8),
-      lock_ds char(32),
-      lock_status_cd char(10) not null,
-      lock_user_nm char(100) not null ,
-      lock_ref char(200),
-      lock_pid char(10),
-      lock_start_dttm num format=E8601DT26.6,
-      lock_end_dttm num format=E8601DT26.6,
-    constraint pk_mp_lockanytable primary key(lock_lib,lock_ds));
-%end;
 %else %do;
   %let msg=lock_anytable given unsupported action (&action);
   %let abortme=1;
diff --git a/base/mp_retainedkey.sas b/base/mp_retainedkey.sas
new file mode 100644
index 0000000..1978006
--- /dev/null
+++ b/base/mp_retainedkey.sas
@@ -0,0 +1,248 @@
+/**
+  @file
+  @brief Generate and apply retained key values to a staging table
+  @details This macro will populate a staging table with a Retained Key based on
+  a business key and a base (target) table.
+
+  Definition of retained key ([source](
+    http://bukhantsov.org/2012/04/what-is-data-vault/)):
+
+  > The retained key is a key which is mapped to business key one-to-one. In
+  > comparison,  the surrogate key includes time and there can be many surrogate
+  > keys corresponding to one business key. This explains the name of the key,
+  > it is retained with insertion of a new version of a row while surrogate key
+  > is increasing.
+
+  This macro is designed to be used as part of a wider load / ETL process (such
+  as the one in [Data Controller for SAS](https://datacontroller.io)).
+
+  Specifically, the macro assumes that the base table has already been 'locked'
+  (eg with the mp_lockanytable.sas macro) prior to invocation.  Also, several
+  tables are assumed to exist (names are configurable):
+
+  @li work.staging_table - the staged data, minus the retained key element
+  @li permlib.base_table - the target table to be loaded (**not** loaded by this
+    macro)
+  @li permlib.maxkeytable - optional, used to store load metaadata.
+  The structure is as follows:
+
+      proc sql;
+      create table yourlib.maxkeytable(
+          keytable varchar(41) label='Base table in libref.dataset format',
+          keycolumn char(32) format=$32.
+            label='The Retained key field containing the key values.',
+          max_key num label=
+            'Integer representing current max RK or SK value in the KEYTABLE',
+          processed_dttm num format=E8601DT26.6
+            label='Datetime this value was last updated',
+        constraint pk_mpe_maxkeyvalues
+            primary key(keytable));
+
+  @param [in] base_lib= (WORK) Libref of the base (target) table.
+  @param [in] base_dsn= (BASETABLE) Name of the base (target) table.
+  @param [in] append_lib= (WORK) Libref of the staging table
+  @param [in] append_dsn= (APPENDTABLE) Name of the staging table
+  @param [in] retained_key= (DEFAULT_RK) Name of RK to generate (should exist on
+    base table)
+  @param [in] business_key= (PK1 PK2) Business key against which to generate
+    RK values.  Should be unique and not null on the staging table.
+  @param [in] check_uniqueness=(NO) Set to yes to perform a uniqueness check.
+    Recommended if there is a chance that the staging data is not unique on the
+    business key.
+  @param [in] maxkeytable= (0) Provide a maxkeytable libds reference here, to
+    store load metadata (maxkey val, load time).  Set to zero if metadata is not
+    required, eg, when preparing a 'dummy' load. Structure is described above.
+    See below for sample data.
+    |KEYTABLE:$32.|KEYCOLUMN:$32.|MAX_KEY:best.|PROCESSED_DTTM:E8601DT26.6|
+    |---|---|---|---|
+    |`DC487173.MPE_SELECTBOX `|`SELECTBOX_RK `|`55 `|`1950427787.8 `|
+    |`DC487173.MPE_FILTERANYTABLE `|`filter_rk `|`14 `|`1951053886.8 `|
+  @param [in] locktable= (0) If updating the maxkeytable, provide the libds
+    reference to the lock table (per mp_lockanytable.sas macro)
+  @param [in] filter_str= Apply a filter - useful for SCD2 or BITEMPORAL loads.
+    Example: `filter_str=%str( (where=( &now < &tech_to)) )`
+  @param [out] outds= (WORK.APPEND) Output table (staging table + retained key)
+
+  <h4> SAS Macros </h4>
+  @li mf_existvar.sas
+  @li mf_getquotedstr.sas
+  @li mf_getuniquename.sas
+  @li mf_nobs.sas
+  @li mp_abort.sas
+  @li mp_lockanytable.sas
+
+  <h4> Related Macros </h4>
+  @li mp_retainedkey.test.sas
+
+  @version 9.2
+
+**/
+
+%macro mp_retainedkey(
+  base_lib=WORK
+  ,base_dsn=BASETABLE
+  ,append_lib=WORK
+  ,append_dsn=APPENDTABLE
+  ,retained_key=DEFAULT_RK
+  ,business_key= PK1 PK2
+  ,check_uniqueness=NO
+  ,maxkeytable=0
+  ,locktable=0
+  ,outds=WORK.APPEND
+  ,filter_str=
+);
+%put &sysmacroname entry vars:;
+%put _local_;
+
+%local base_libds app_libds key_field check maxkey idx_pk newkey_cnt iserr
+  msg x tempds1 tempds2 comma_pk appnobs checknobs dropvar tempvar idx_val;
+%let base_libds=%upcase(&base_lib..&base_dsn);
+%let app_libds=%upcase(&append_lib..&append_dsn);
+%let tempds1=%mf_getuniquename();
+%let tempds2=%mf_getuniquename();
+%let comma_pk=%mf_getquotedstr(in_str=%str(&business_key),dlm=%str(,),quote=);
+
+/* validation checks */
+%let iserr=0;
+%if &syscc>0 %then %do;
+  %let iserr=1;
+  %let msg=%str(SYSCC=&syscc on macro entry);
+%end;
+%else %if %sysfunc(exist(&base_libds))=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Base LIBDS (&base_libds) expected but NOT FOUND);
+%end;
+%else %if %sysfunc(exist(&app_libds))=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Append LIBDS (&app_libds) expected but NOT FOUND);
+%end;
+%else %if &maxkeytable ne 0 and %sysfunc(exist(&maxkeytable))=0  %then %do;
+  %let iserr=1;
+  %let msg=%str(Maxkeytable (&maxkeytable) expected but NOT FOUND);
+%end;
+%else %if &maxkeytable ne 0 and %sysfunc(exist(&locktable))=0  %then %do;
+  %let iserr=1;
+  %let msg=%str(Locktable (&locktable) expected but NOT FOUND);
+%end;
+%else %if %length(&business_key)=0 %then %do;
+  %let iserr=1;
+  %let msg=%str(Business key (&business_key) expected but NOT FOUND);
+%end;
+
+%do x=1 %to %sysfunc(countw(&business_key));
+  /* check business key values exist */
+  %let key_field=%scan(&business_key,&x,%str( ));
+  %if (not %mf_existvar(&app_libds,&key_field))
+    or (not %mf_existvar(&base_libds,&key_field))
+  %then %do;
+    %let iserr=1;
+    %let msg=Business key (&key_field) not found!;
+  %end;
+%end;
+
+%if &iserr=1 %then %do;
+  /* err case so first perform an unlock of the base table before exiting */
+  %mp_lockanytable(
+    UNLOCK,lib=&base_lib,ds=&base_dsn,ref=%superq(msg),ctl_ds=&locktable
+  )
+%end;
+%mp_abort(iftrue=(&iserr=1),mac=mp_retainedkey,msg=%superq(msg))
+
+proc sql noprint;
+select sum(max(&retained_key),0) into: maxkey from &base_libds;
+
+/**
+  * get base table RK and bus field values for lookup
+  */
+proc sql noprint;
+create table &tempds1 as
+  select distinct &comma_pk,&retained_key
+  from &base_libds &filter_str
+  order by &comma_pk,&retained_key;
+
+%if &check_uniqueness=YES %then %do;
+  select count(*) into:checknobs
+    from (select distinct &comma_pk from &app_libds);
+  select count(*) into: appnobs from &app_libds; /* might be view */
+  %if &checknobs ne &appnobs %then %do;
+    %let msg=Source table &app_libds is not unique on (&business_key);
+    %let iserr=1;
+  %end;
+%end;
+%if &iserr=1 %then %do;
+  /* err case so first perform an unlock of the base table before exiting */
+  %mp_lockanytable(
+    UNLOCK,lib=&base_lib,ds=&base_dsn,ref=%superq(msg),ctl_ds=&locktable
+  )
+%end;
+%mp_abort(iftrue= (&iserr=1),mac=mp_retainedkey,msg=%superq(msg))
+
+%if %mf_existvar(&app_libds,&retained_key)
+%then %let dropvar=(drop=&retained_key);
+
+/* prepare interim table with retained key populated for matching keys */
+proc sql noprint;
+create table &tempds2 as
+  select b.&retained_key, a.*
+  from &app_libds &dropvar a
+  left join &tempds1 b
+  on 1
+  %do idx_pk=1 %to %sysfunc(countw(&business_key));
+    %let idx_val=%scan(&business_key,&idx_pk);
+    and a.&idx_val=b.&idx_val
+  %end;
+  order by &retained_key;
+
+/* identify the number of entries without retained keys (new records) */
+select count(*) into: newkey_cnt
+  from &tempds2
+  where missing(&retained_key);
+quit;
+
+/**
+  * Update maxkey table if link provided
+  */
+%if &maxkeytable ne 0 %then %do;
+  proc sql;
+  select count(*) into: check from &maxkeytable
+    where upcase(keytable)="&base_libds";
+
+  %mp_lockanytable(LOCK
+    ,lib=%scan(&maxkeytable,1,.)
+    ,ds=%scan(&maxkeytable,2,.)
+    ,ref=Updating maxkeyvalues with mp_retainedkey
+    ,ctl_ds=&locktable
+  )
+  proc sql;
+  %if &check=0 %then %do;
+  insert into &maxkeytable
+    set keytable="&base_libds"
+      ,keycolumn="&retained_key"
+      ,max_key=%eval(&maxkey+&newkey_cnt)
+      ,processed_dttm="%sysfunc(datetime(),E8601DT26.6)"dt;
+  %end;
+  %else %do;
+  update &maxkeytable
+    set max_key=%eval(&maxkey+&newkey_cnt)
+      ,processed_dttm="%sysfunc(datetime(),E8601DT26.6)"dt
+    where keytable="&base_libds";
+  %end;
+  %mp_lockanytable(UNLOCK
+    ,lib=%scan(&maxkeytable,1,.)
+    ,ds=%scan(&maxkeytable,2,.)
+    ,ref=Updating maxkeyvalues with maxkey=%eval(&maxkey+&newkey_cnt)
+    ,ctl_ds=&locktable
+  )
+%end;
+
+/* fill in the missing retained key values */
+%let tempvar=%mf_getuniquename();
+data &outds(drop=&tempvar);
+  retain &tempvar %eval(&maxkey+1);
+  set &tempds2;
+  if &retained_key =. then &retained_key=&tempvar;
+  &tempvar=&tempvar+1;
+run;
+
+%mend mp_retainedkey;
+
diff --git a/tests/crossplatform/mp_retainedkey.test.sas b/tests/crossplatform/mp_retainedkey.test.sas
new file mode 100644
index 0000000..5c33bac
--- /dev/null
+++ b/tests/crossplatform/mp_retainedkey.test.sas
@@ -0,0 +1,116 @@
+/**
+  @file
+  @brief Testing mp_retainedkey macro
+
+  <h4> SAS Macros </h4>
+  @li mp_assert.sas
+  @li mp_assertcolvals.sas
+  @li mp_retainedkey.sas
+
+**/
+
+/**
+  * Setup base tables
+  */
+proc sql;
+create table work.maxkeytable(
+    keytable varchar(41) label='Base table in libref.dataset format',
+    keycolumn char(32) format=$32.
+      label='The Retained key field containing the key values.',
+    max_key num label=
+      'Integer representing current max RK or SK value in the KEYTABLE',
+    processed_dttm num format=E8601DT26.6
+      label='Datetime this value was last updated',
+  constraint pk_mpe_maxkeyvalues
+      primary key(keytable));
+
+create table work.locktable(
+    lock_lib char(8),
+    lock_ds char(32),
+    lock_status_cd char(10) not null,
+    lock_user_nm char(100) not null ,
+    lock_ref char(200),
+    lock_pid char(10),
+    lock_start_dttm num format=E8601DT26.6,
+    lock_end_dttm num format=E8601DT26.6,
+  constraint pk_mp_lockanytable primary key(lock_lib,lock_ds));
+
+data work.targetds;
+  rk_col=_n_;
+  set sashelp.class;
+run;
+
+data work.appendtable;
+  set sashelp.class;
+  if mod(_n_,2)=0 then name=cats('New',_n_);
+  if _n_<7;
+run;
+
+libname x (work);
+
+/** Test 1 - base case **/
+%mp_retainedkey(
+  base_lib=X
+  ,base_dsn=targetds
+  ,append_lib=X
+  ,append_dsn=APPENDTABLE
+  ,retained_key=rk_col
+  ,business_key= name
+  ,check_uniqueness=NO
+  ,maxkeytable=0
+  ,locktable=0
+  ,outds=work.APPEND
+  ,filter_str=
+)
+%mp_assert(
+  iftrue=(&syscc=0),
+  desc=Checking errors in test 1,
+  outds=work.test_results
+)
+
+data work.check;
+  do val=1,3,5,20,21,22;
+    output;
+  end;
+run;
+%mp_assertcolvals(work.append.rk_col,
+  checkvals=work.check.val,
+  desc=All values have a match,
+  test=ALLVALS
+)
+
+/** Test 2 - all new records, with metadata logging and unique check **/
+data work.targetds2;
+  rk_col=_n_;
+  set sashelp.class;
+run;
+
+data work.appendtable2;
+  set sashelp.class;
+  do x=1 to 21;
+    name=cats('New',x);
+    output;
+  end;
+  stop;
+run;
+
+%mp_retainedkey(base_dsn=targetds2
+  ,append_dsn=APPENDTABLE2
+  ,retained_key=rk_col
+  ,business_key= name
+  ,check_uniqueness=YES
+  ,maxkeytable=x.maxkeytable
+  ,locktable=work.locktable
+  ,outds=WORK.APPEND2
+  ,filter_str=
+)
+%mp_assert(
+  iftrue=(&syscc=0),
+  desc=Checking errors in test 2,
+  outds=work.test_results
+)
+%mp_assert(
+  iftrue=(%mf_nobs(work.append2)=21),
+  desc=Checking append records created,
+  outds=work.test_results
+)