diff --git a/docs/ascii-protocol/ch02-collection-items.md b/docs/ascii-protocol/ch02-collection-items.md
index 40da2417..7d0f2c64 100644
--- a/docs/ascii-protocol/ch02-collection-items.md
+++ b/docs/ascii-protocol/ch02-collection-items.md
@@ -73,7 +73,7 @@ B+tree collection에서 사용가능한 bkey 데이터 유형은 아래 두 가
 
   "0x"로 시작하는 짝수 개의 hexadecimal 문자열로 표현하며, 대소문자 모두 사용 가능하다.
   ARCUS cache server는 두 hexadecimal 문자를 1 byte로 저장하며,
-  1 ~ 31 길이의 variable length byte array로 저장한다.
+  1 ~ 63 길이의 variable length byte array로 저장한다.
 
   hexadecimal 표현이 올바른 경우의 저장 바이트 수와 잘못된 경우의 이유는 아래와 같다.
 
diff --git a/docs/ascii-protocol/ch03-item-attributes.md b/docs/ascii-protocol/ch03-item-attributes.md
index 7d273926..761426d6 100644
--- a/docs/ascii-protocol/ch03-item-attributes.md
+++ b/docs/ascii-protocol/ch03-item-attributes.md
@@ -34,7 +34,7 @@ ARCUS Cache Server는 collection 기능 지원으로 인해,
 | readable       | collection  | readable/unreadable   | "on", "off"                    | "on"                    |
 |-----------------------------------------------------------------------------------------------------------------|
 | maxbkeyrange   | b+tree only | maximum bkey range    | 8 bytes unsigned integer or    | 0                       |
-|                |             |                       | hexadecimal (max 31 bytes)     |                         |
+|                |             |                       | hexadecimal (max 63 bytes)     |                         |
 |-----------------------------------------------------------------------------------------------------------------|
 ```
 
diff --git a/engines/default/cmdlogrec.c b/engines/default/cmdlogrec.c
index 94f8a65b..7c64f063 100644
--- a/engines/default/cmdlogrec.c
+++ b/engines/default/cmdlogrec.c
@@ -353,7 +353,7 @@ static void lrec_it_link_print(LogRec *logrec)
     struct lrec_item_common *cm = (struct lrec_item_common*)&body->cm;
     char *keyptr = body->data;
 
-    char metastr[180];
+    char metastr[MAX_BKEY_LENG*2 + 90];
     if (cm->ittype == ITEM_TYPE_KV) {
         sprintf(metastr, "cas=%"PRIu64, body->ptr.cas);
     } else {
@@ -1042,8 +1042,8 @@ static void lrec_bt_elem_insert_print(LogRec *logrec)
     unsigned char *eflagptr = bkeyptr + real_nbkey;
     char *attrptr = (char*)(eflagptr + log->body.neflag + log->body.vallen);
 
-    char bkeystr[90];
-    char eflagstr[90];
+    char bkeystr[MAX_BKEY_LENG*2 + 20];
+    char eflagstr[MAX_EFLAG_LENG*2 + 20];
     char attrstr[180];
     lrec_bkey_print(log->body.nbkey, bkeyptr, bkeystr);
     if (log->body.neflag > 0) {
@@ -1110,7 +1110,7 @@ static void lrec_bt_elem_delete_print(LogRec *logrec)
     char *keyptr = log->body.data;
     unsigned char *bkeyptr = (unsigned char*)(keyptr + log->body.keylen);
 
-    char bkeystr[90];
+    char bkeystr[MAX_BKEY_LENG*2 + 20];
     lrec_bkey_print(log->body.nbkey, bkeyptr, bkeystr);
     lrec_header_print(&log->header);
     fprintf(stderr, "[BODY  ] keylen=%u | keystr=%.*s | bkey=%s | drop=%s\r\n",
@@ -1210,8 +1210,8 @@ static void lrec_bt_elem_delete_logical_print(LogRec *logrec)
     char *fbkeyptr = keyptr + log->body.keylen;
     char *tbkeyptr = fbkeyptr + BTREE_REAL_NBKEY(log->body.from_nbkey);
 
-    char fbkeystr[90];
-    char tbkeystr[90];
+    char fbkeystr[MAX_BKEY_LENG*2 + 20];
+    char tbkeystr[MAX_BKEY_LENG*2 + 20];
     lrec_bkey_print(log->body.from_nbkey, (unsigned char *)fbkeyptr, fbkeystr);
     lrec_bkey_print(log->body.to_nbkey, (unsigned char*)tbkeyptr, tbkeystr);
 
@@ -1337,8 +1337,8 @@ static void lrec_snapshot_elem_link_print(LogRec *logrec)
                 body->nekey, body->nekey, valptr,
                 body->nbytes, (body->nbytes-2 <= 250 ? body->nbytes-2 : 250), (valptr + body->nekey));
     } else if (log->header.updtype == UPD_BT_ELEM_INSERT) {
-        char bkeystr[90];
-        char eflagstr[90];
+        char bkeystr[MAX_BKEY_LENG*2 + 20];
+        char eflagstr[MAX_EFLAG_LENG*2 + 20];
         unsigned char *bkeyptr = (unsigned char*)valptr;
         unsigned char *eflagptr = (unsigned char*)(valptr + BTREE_REAL_NBKEY(body->nekey));
         lrec_bkey_print(body->nekey, bkeyptr, bkeystr);
diff --git a/include/memcached/types.h b/include/memcached/types.h
index 97222863..aa828ee5 100644
--- a/include/memcached/types.h
+++ b/include/memcached/types.h
@@ -288,8 +288,8 @@ extern "C" {
      * bkey and eflag
      */
 #define MIN_BKEY_LENG  1
-#define MAX_BKEY_LENG  31
-#define MAX_EFLAG_LENG 31
+#define MAX_BKEY_LENG  63
+#define MAX_EFLAG_LENG 63
 #define MAX_FIELD_LENG 250
 #define BKEY_NULL  255
 #define EFLAG_NULL 255
diff --git a/lqdetect.c b/lqdetect.c
index 57ce5113..0fe81753 100644
--- a/lqdetect.c
+++ b/lqdetect.c
@@ -10,7 +10,7 @@
 #include "memcached/util.h"
 
 #define LQ_THRESHOLD_DEFAULT 4000
-#define LQ_QUERY_SIZE  (64*2+64) /* bop get (longest query) : "<longest bkey>..<longest bkey> efilter <offset> <count> delete" */
+#define LQ_QUERY_SIZE  (MAX_BKEY_LENG*2*2+64) /* bop get (longest query) : "<longest bkey>..<longest bkey> efilter <offset> <count> delete" */
 #define LQ_KEY_SIZE    250       /* the max size of key string */
 #define LQ_SAVE_CNT    20        /* save key count */
 #define LQ_INPUT_SIZE  500       /* the size of input(time, ip, command, argument) */
diff --git a/memcached.c b/memcached.c
index 22203951..67a76e7f 100644
--- a/memcached.c
+++ b/memcached.c
@@ -13272,10 +13272,9 @@ static int try_read_command_ascii(conn *c)
             }
             /* Check KEY_MAX_LENGTH and eflag filter length
              *  - KEY_MAX_LENGTH : 16000
-             *  - IN eflag filter : > 6400 (64*100)
+             *  - IN eflag filter : > 12800 (128*100)
              */
-            if (c->rbytes > ((16+8)*1024)) {
-                /* The length of "stats prefixes" command cannot exceed 24 KB. */
+            if (c->rbytes > ((16+16)*1024)) {
                 if (strncmp(ptr, "get ", 4) && strncmp(ptr, "gets ", 5)) {
                     char buffer[16];
                     memcpy(buffer, ptr, 15); buffer[15] = '\0';
diff --git a/t/coll_bop_delete.t b/t/coll_bop_delete.t
index 9a15c166..25c92588 100644
--- a/t/coll_bop_delete.t
+++ b/t/coll_bop_delete.t
@@ -24,7 +24,7 @@ bop delete bkey1 0..0xFF: CLIENT_ERROR bad command line format
 bop delete bkey1 0x00..0xFFF: CLIENT_ERROR bad command line format
 bop delete bkey1 0x11..0xFFFF: NOT_FOUND_ELEMENT
 bop delete bkey1 0x00..0xFF 1 EQ 0x05: NOT_FOUND_ELEMENT
-bop delete bkey1 0x00..0xFF 32 EQ 0x05: CLIENT_ERROR bad command line format
+bop delete bkey1 0x00..0xFF 64 EQ 0x05: CLIENT_ERROR bad command line format
 bop delete bkey1 0x00..0xFF 1 XX 0x05: CLIENT_ERROR bad command line format
 bop delete bkey1 0x00..0xFF 0 & 0xFFFFFF EQ 0x03: CLIENT_ERROR bad command line format
 bop delete bkey1 0x00..0xFF 0 & 0xFFFFFF EQ 0x030303: NOT_FOUND_ELEMENT
@@ -115,7 +115,7 @@ $cmd = "bop delete bkey1 0x11..0xFFFF"; $rst = "NOT_FOUND_ELEMENT";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop delete bkey1 0x00..0xFF 1 EQ 0x05"; $rst = "NOT_FOUND_ELEMENT";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop delete bkey1 0x00..0xFF 32 EQ 0x05"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop delete bkey1 0x00..0xFF 64 EQ 0x05"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop delete bkey1 0x00..0xFF 1 XX 0x05"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
diff --git a/t/coll_bop_insert.t b/t/coll_bop_insert.t
index 83d96500..ad33a576 100644
--- a/t/coll_bop_insert.t
+++ b/t/coll_bop_insert.t
@@ -43,11 +43,11 @@ datum1
 setattr bkey1 maxcount=4000
 bop insert bkey1 0x020 6
 datum2
-bop insert bkey1 0x0202020202020202020202020202020202020202020202020202020202020202 6
+bop insert bkey1 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6
 datum2
 bop insert bkey1 0x0202 0x020 6
 datum2
-bop insert bkey1 0x0202 0x0202020202020202020202020202020202020202020202020202020202020202 6
+bop insert bkey1 0x0202 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6
 datum2
 bop insert bkey1 0x0202 02 6
 datum2
@@ -130,11 +130,11 @@ $cmd = "setattr bkey1 maxcount=4000"; $rst = "OK";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop insert bkey1 0x020 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop insert bkey1 0x0202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop insert bkey1 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop insert bkey1 0x0202 0x020 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop insert bkey1 0x0202 0x0202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop insert bkey1 0x0202 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop insert bkey1 0x0202 02 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
diff --git a/t/coll_bop_update.t b/t/coll_bop_update.t
index 206f0dd7..71eafb28 100644
--- a/t/coll_bop_update.t
+++ b/t/coll_bop_update.t
@@ -96,7 +96,7 @@ datum2
 bop update bkey2 0x20 1 | 0xFF -1
 bop update bkey2 0x0020 1 | 0xFF -1
 bop update bkey2 0x0040 4 | 0xFF -1
-bop update bkey2 0x0040 32 | 0xFF -1
+bop update bkey2 0x0040 64 | 0xFF -1
 
 delete bkey1
 delete bkey2
@@ -325,7 +325,7 @@ $cmd = "bop update bkey2 0x0020 1 | 0xFF -1"; $rst = "EFLAG_MISMATCH";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop update bkey2 0x0040 4 | 0xFF -1"; $rst = "EFLAG_MISMATCH";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop update bkey2 0x0040 32 | 0xFF -1"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop update bkey2 0x0040 64 | 0xFF -1"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 
 # Finalize
diff --git a/t/coll_bop_upsert.t b/t/coll_bop_upsert.t
index f9ee8724..08f88431 100644
--- a/t/coll_bop_upsert.t
+++ b/t/coll_bop_upsert.t
@@ -44,11 +44,11 @@ datum1
 setattr bkey1 maxcount=4000
 bop upsert bkey1 0x020 6
 datum2
-bop upsert bkey1 0x0202020202020202020202020202020202020202020202020202020202020202 6
+bop upsert bkey1 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6
 datum2
 bop upsert bkey1 0x0202 0x020 6
 datum2
-bop upsert bkey1 0x0202 0x0202020202020202020202020202020202020202020202020202020202020202 6
+bop upsert bkey1 0x0202 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6
 datum2
 bop upsert bkey1 0x0202 02 6
 datum2
@@ -131,11 +131,11 @@ $cmd = "setattr bkey1 maxcount=4000"; $rst = "OK";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop upsert bkey1 0x020 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop upsert bkey1 0x0202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop upsert bkey1 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop upsert bkey1 0x0202 0x020 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
-$cmd = "bop upsert bkey1 0x0202 0x0202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
+$cmd = "bop upsert bkey1 0x0202 0x02020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202020202 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);
 $cmd = "bop upsert bkey1 0x0202 02 6"; $rst = "CLIENT_ERROR bad command line format";
 mem_cmd_is($sock, $cmd, "", $rst);