diff --git a/src/obiavl.c b/src/obiavl.c
index 5d31bab..eea42a5 100644
--- a/src/obiavl.c
+++ b/src/obiavl.c
@@ -969,7 +969,7 @@ int add_new_avl_in_group(OBIDMS_avl_group_p avl_group)
 	(avl_group->current_avl_idx)++;
 
 	// Create the new AVL
-	(avl_group->sub_avls)[avl_group->current_avl_idx] = obi_create_avl(avl_group->dms, avl_group->avl_name, avl_group->current_avl_idx);
+	(avl_group->sub_avls)[avl_group->current_avl_idx] = obi_create_avl(avl_group->dms, avl_group->name, avl_group->current_avl_idx);
 	if ((avl_group->sub_avls)[avl_group->current_avl_idx] == NULL)
 	{
 		obidebug(1, "\nError creating a new AVL tree in a group");
@@ -1611,11 +1611,6 @@ OBIDMS_avl_p obi_create_avl(OBIDMS_p dms, const char* avl_name, int avl_idx)
 	// Bloom filter
 	bloom_init(&((avl->header)->bloom_filter), MAX_NODE_COUNT_PER_AVL);
 
-	// Add in the list of opened AVL trees
-	*(((dms->opened_indexers)->indexers)+((dms->opened_indexers)->nb_opened_indexers)) = avl;
-	((dms->opened_indexers)->nb_opened_indexers)++;
-	avl->counter = 1;
-
 	if (avl_idx >= 0)
 		free(complete_avl_name);
 
@@ -1636,7 +1631,6 @@ OBIDMS_avl_p obi_open_avl(OBIDMS_p dms, const char* avl_name, int avl_idx)
 	int					avl_dir_file_descriptor;
 	OBIDMS_avl_data_p   avl_data;
 	OBIDMS_avl_p		avl;
-	size_t 				i;
 
 	// Get complete name of AVL if index
 	if (avl_idx >= 0)
@@ -1657,18 +1651,6 @@ OBIDMS_avl_p obi_open_avl(OBIDMS_p dms, const char* avl_name, int avl_idx)
 		strcpy(complete_avl_name, avl_name);
 	}
 
-	// Check if the AVL tree is already in the list of opened AVL trees
-	for (i=0; i < ((dms->opened_indexers)->nb_opened_indexers); i++)
-	{
-		if (!strcmp(((*(((dms->opened_indexers)->indexers)+i))->header)->avl_name, complete_avl_name))
-		{	// Found the AVL tree already opened
-			((*(((dms->opened_indexers)->indexers)+i))->counter)++;
-			if (avl_idx >= 0)
-				free(complete_avl_name);
-			return *(((dms->opened_indexers)->indexers)+i);
-		}
-	}
-
     // Open the AVL directory
 	avl_dir_name = get_full_path_of_avl_dir(dms, avl_name);
 	if (avl_dir_name == NULL)
@@ -1877,11 +1859,6 @@ OBIDMS_avl_p obi_open_avl(OBIDMS_p dms, const char* avl_name, int avl_idx)
 	avl->dir_fd    = avl_dir_file_descriptor;
 	avl->avl_fd    = avl_file_descriptor;
 
-	// Add in the list of opened AVL trees
-	*(((dms->opened_indexers)->indexers)+((dms->opened_indexers)->nb_opened_indexers)) = avl;
-	((dms->opened_indexers)->nb_opened_indexers)++;
-	avl->counter = 1;
-
 	if (avl_idx >= 0)
 		free(complete_avl_name);
 
@@ -1929,10 +1906,16 @@ OBIDMS_avl_group_p obi_create_avl_group(OBIDMS_p dms, const char* avl_name)
 	}
 
 	avl_group->current_avl_idx = 0;
-	strcpy(avl_group->avl_name, avl_name);
+	strcpy(avl_group->name, avl_name);
 
 	avl_group->dms = dms;
 
+	// Add in the list of open indexers
+	obi_dms_list_indexer(dms, avl_group);
+
+	// Set counter to 1
+	avl_group->counter = 1;
+
 	return avl_group;
 }
 
@@ -1944,7 +1927,14 @@ OBIDMS_avl_group_p obi_open_avl_group(OBIDMS_p dms, const char* avl_name)
 	int					avl_count;
 	int					i;
 
-	// TODO check that the group isn't already open
+	// Check if the group isn't already open
+	avl_group = obi_dms_get_indexer_from_list(dms, avl_name);
+	if (avl_group != NULL)	// Found it
+	{
+		// Increment counter
+		(avl_group->counter)++;
+		return avl_group;
+	}
 
 	avl_group = (OBIDMS_avl_group_p) malloc(sizeof(OBIDMS_avl_group_t));
 	if (avl_group == NULL)
@@ -1973,10 +1963,16 @@ OBIDMS_avl_group_p obi_open_avl_group(OBIDMS_p dms, const char* avl_name)
 			return NULL;
 	}
 	avl_group->current_avl_idx = avl_count-1;			// TODO latest. discuss
-	strcpy(avl_group->avl_name, avl_name);
+	strcpy(avl_group->name, avl_name);
 
 	avl_group->dms = dms;
 
+	// Add in the list of open indexers
+	obi_dms_list_indexer(dms, avl_group);
+
+	// Set counter to 1
+	avl_group->counter = 1;
+
 	return avl_group;
 }
 
@@ -1984,51 +1980,29 @@ OBIDMS_avl_group_p obi_open_avl_group(OBIDMS_p dms, const char* avl_name)
 int obi_close_avl(OBIDMS_avl_p avl)
 {
 	int                 	ret_val = 0;
-	size_t             		i;
-	Opened_indexers_list_p  indexers_list;
-	OBIDMS_p        	    dms;
 
-	dms = avl->dms;
+	ret_val = close_avl_data(avl->data);
 
-	indexers_list = dms->opened_indexers;
+	ret_val = truncate_avl_to_size_used(avl);
 
-	(avl->counter)--;
-
-	if (avl->counter == 0)
+	if (munmap(avl->tree, (((avl->header)->nb_items_max) * sizeof(AVL_node_t))) < 0)
 	{
-		// Delete from the list of opened avls
-		for (i=0; i < (indexers_list->nb_opened_indexers); i++)
-		{
-			if (!strcmp(((*((indexers_list->indexers)+i))->header)->avl_name, (avl->header)->avl_name))
-			{	// Found the avl. Rearrange list
-				(indexers_list->nb_opened_indexers)--;
-				(indexers_list->indexers)[i] = (indexers_list->indexers)[indexers_list->nb_opened_indexers];
-			}
-		}
-
-		ret_val = close_avl_data(avl->data);
-
-		ret_val = truncate_avl_to_size_used(avl);
-
-		if (munmap(avl->tree, (((avl->header)->nb_items_max) * sizeof(AVL_node_t))) < 0)
-		{
-			obi_set_errno(OBI_AVL_ERROR);
-			obidebug(1, "\nError munmapping the tree of an AVL tree file");
-			ret_val = -1;
-		}
-
-		if (munmap(avl->header, (avl->header)->header_size) < 0)
-		{
-			obi_set_errno(OBI_AVL_ERROR);
-			obidebug(1, "\nError munmapping the header of an AVL tree file");
-			ret_val = -1;
-		}
-
-		close(avl->avl_fd);
-
-		free(avl);
+		obi_set_errno(OBI_AVL_ERROR);
+		obidebug(1, "\nError munmapping the tree of an AVL tree file");
+		ret_val = -1;
 	}
 
+	if (munmap(avl->header, (avl->header)->header_size) < 0)
+	{
+		obi_set_errno(OBI_AVL_ERROR);
+		obidebug(1, "\nError munmapping the header of an AVL tree file");
+		ret_val = -1;
+	}
+
+	close(avl->avl_fd);
+
+	free(avl);
+
 	return ret_val;
 }
 
@@ -2040,10 +2014,21 @@ int obi_close_avl_group(OBIDMS_avl_group_p avl_group)
 
 	ret_val = 0;
 
-	for (i=0; i < (avl_group->current_avl_idx); i++)
-		if (obi_close_avl((avl_group->sub_avls)[i]) < 0)
-			ret_val = -1;
-	free(avl_group);
+	(avl_group->counter)--;
+
+	if (avl_group->counter == 0)
+	{
+		// Delete from the list of opened indexers
+		ret_val = obi_dms_unlist_indexer(avl_group->dms, avl_group);
+
+		// Close each AVL of the group
+		for (i=0; i < (avl_group->current_avl_idx); i++)
+			if (obi_close_avl((avl_group->sub_avls)[i]) < 0)
+				ret_val = -1;
+
+		free(avl_group);
+	}
+
 	return ret_val;
 }
 
diff --git a/src/obiavl.h b/src/obiavl.h
index 0e8547e..79150e2 100644
--- a/src/obiavl.h
+++ b/src/obiavl.h
@@ -152,8 +152,6 @@ typedef struct OBIDMS_avl {
 													 	 	 */
 	int							avl_fd;						/**< The file descriptor of the file containing the AVL tree.
 													 	 	 */
-	size_t						counter;					/**< Indicates by how many threads/programs (TODO) the AVL tree is used.
-													 	 	 */
 } OBIDMS_avl_t, *OBIDMS_avl_p;
 
 
@@ -165,10 +163,12 @@ typedef struct OBIDMS_avl_group {
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 */
 	int 			current_avl_idx;						/**< Index in the sub_avls array of the AVL tree currently being filled.
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 */
-	char			avl_name[AVL_MAX_NAME+1];			 	/**< Base name of the AVL group. The AVL trees in it have names of the form basename_idx.
+	char			name[AVL_MAX_NAME+1];				 	/**< Base name of the AVL group. The AVL trees in it have names of the form basename_idx.
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 */
 	OBIDMS_p        dms;									/**< Pointer to the OBIDMS structure to which the AVL group belongs.
 	 	 	 	 	 	 	 	 	 	 	 	 	 	 	 */
+	size_t			counter;								/**< Indicates by how many threads/programs (TODO) the AVL group is used.
+													 	 	 */
 } OBIDMS_avl_group_t, *OBIDMS_avl_group_p;
 
 
diff --git a/src/obiblob_indexer.h b/src/obiblob_indexer.h
index 9bc744d..dab9099 100644
--- a/src/obiblob_indexer.h
+++ b/src/obiblob_indexer.h
@@ -27,7 +27,9 @@
  	 	 	 	 	 	 	 	 	 	 	 	 */
 
 
-typedef OBIDMS_avl_group_p Obi_indexer_p; 		/**< Typedef to refer to the used indexer structure.
+typedef struct OBIDMS_avl_group Obi_indexer;	/**< Typedef to refer to the used indexer structure.
+ 	 	 	 	 	 	 	 	 	 	 	 	 */
+typedef OBIDMS_avl_group_p Obi_indexer_p; 		/**< Typedef to refer to the pointer of the used indexer structure.
  	 	 	 	 	 	 	 	 	 	 	 	 */
 
 
diff --git a/src/obidms.c b/src/obidms.c
index 04ed33a..c8ef28d 100644
--- a/src/obidms.c
+++ b/src/obidms.c
@@ -23,6 +23,7 @@
 #include "obierrno.h"
 #include "obidebug.h"
 #include "obidmscolumn.h"
+#include "obiblob_indexer.h"
 #include "utils.h"
 #include "obilittlebigman.h"
 
@@ -417,12 +418,10 @@ OBIDMS_p obi_open_dms(const char* dms_name)
 
 	// Initialize the list of opened columns
 	dms->opened_columns = (Opened_columns_list_p) malloc(sizeof(Opened_columns_list_t));
-	(dms->opened_columns)->columns = (OBIDMS_column_p*) malloc(MAX_NB_OPENED_COLUMNS*sizeof(OBIDMS_column_p));
 	(dms->opened_columns)->nb_opened_columns = 0;
 
 	// Initialize the list of opened indexers	// TODO should be handled somewhere else?
 	dms->opened_indexers = (Opened_indexers_list_p) malloc(sizeof(Opened_indexers_list_t));
-	(dms->opened_indexers)->indexers = (OBIDMS_avl_p*) malloc(MAX_NB_OPENED_INDEXERS*sizeof(OBIDMS_avl_p));		// TODO idk how to handle this
 	(dms->opened_indexers)->nb_opened_indexers = 0;
 
 	return dms;
@@ -477,3 +476,165 @@ int obi_close_dms(OBIDMS_p dms)
 	return 0;
 }
 
+
+int obi_dms_is_column_name_in_list(OBIDMS_p dms, const char* column_name)
+{
+	int i;
+	Opened_columns_list_p columns_list;
+
+	columns_list = dms->opened_columns;
+
+	for (i=0; i < (columns_list->nb_opened_columns); i++)
+	{
+		if (!strcmp(((*((columns_list->columns)+i))->header)->name, column_name))
+		{	// Found it
+			return 0;
+		}
+	}
+	return 1;
+}
+
+
+OBIDMS_column_p obi_dms_get_column_from_list(OBIDMS_p dms, const char* column_name, obiversion_t version)
+{
+	int i;
+
+	for (i=0; i < ((dms->opened_columns)->nb_opened_columns); i++)
+	{
+		if (!strcmp(((*(((dms->opened_columns)->columns)+i))->header)->name, column_name)
+				&& (((*(((dms->opened_columns)->columns)+i))->header)->version == version))
+		{	// Found the column already opened, return it
+			return *(((dms->opened_columns)->columns)+i);
+		}
+	}
+	// Didn't find the column
+	return NULL;
+}
+
+
+void obi_dms_list_column(OBIDMS_p dms, OBIDMS_column_p column)
+{
+	*(((dms->opened_columns)->columns)+((dms->opened_columns)->nb_opened_columns)) = column;
+	((dms->opened_columns)->nb_opened_columns)++;
+}
+
+
+int obi_dms_unlist_column(OBIDMS_p dms, OBIDMS_column_p column)
+{
+	int i;
+	Opened_columns_list_p columns_list;
+
+	columns_list = dms->opened_columns;
+
+	for (i=0; i < columns_list->nb_opened_columns; i++)
+	{
+		if (!strcmp(((*((columns_list->columns)+i))->header)->name, (column->header)->name)
+				&& (((*((columns_list->columns)+i))->header)->version == (column->header)->version))
+		{	// Found the column. Rearrange list
+			(columns_list->nb_opened_columns)--;
+			(columns_list->columns)[i] = (columns_list->columns)[columns_list->nb_opened_columns];
+			return 0;
+		}
+	}
+
+	obidebug(1, "\nCould not find the column to delete from list of open columns");
+	return -1;
+}
+
+
+Obi_indexer_p obi_dms_get_indexer_from_list(OBIDMS_p dms, const char* indexer_name)
+{
+	int i;
+	Opened_indexers_list_p indexers_list;
+
+	indexers_list = dms->opened_indexers;
+
+	for (i=0; i < (indexers_list->nb_opened_indexers); i++)
+	{
+		if (!strcmp(((indexers_list->indexers)[i])->name, indexer_name))	// TODO it references something in AVL_group struct
+		{	// Found the indexer already opened, return it
+			return (indexers_list->indexers)[i];
+		}
+	}
+	// Didn't find the indexer
+	return NULL;
+}
+
+
+void obi_dms_list_indexer(OBIDMS_p dms, Obi_indexer_p indexer)
+{
+	*(((dms->opened_indexers)->indexers)+((dms->opened_indexers)->nb_opened_indexers)) = indexer;
+	((dms->opened_indexers)->nb_opened_indexers)++;
+}
+
+
+int obi_dms_unlist_indexer(OBIDMS_p dms, Obi_indexer_p indexer)
+{
+	int i;
+	Opened_indexers_list_p indexers_list;
+
+	indexers_list = dms->opened_indexers;
+
+	for (i=0; i < indexers_list->nb_opened_indexers; i++)
+	{
+		if (!strcmp(((indexers_list->indexers)[i])->name, indexer->name))	// TODO it references something in AVL_group struct
+		{	// Found the indexer. Rearrange list
+			(indexers_list->nb_opened_indexers)--;
+			(indexers_list->indexers)[i] = (indexers_list->indexers)[indexers_list->nb_opened_indexers];
+			return 0;
+		}
+	}
+
+	obidebug(1, "\nCould not find the indexer to delete from list of open indexers");
+	return -1;
+}
+
+
+char* get_full_path(OBIDMS_p dms, const char* path_name)
+{
+	char* full_path;
+
+	full_path = (char*) malloc((MAX_PATH_LEN)*sizeof(char));
+	if (full_path == NULL)
+	{
+		obi_set_errno(OBI_MALLOC_ERROR);
+		obidebug(1, "\nError allocating memory for the char* path to a file or directory");
+		return NULL;
+	}
+
+	if (getcwd(full_path, MAX_PATH_LEN) == NULL)
+	{
+		obi_set_errno(OBI_UTILS_ERROR);
+		obidebug(1, "\nError getting the path to a file or directory");
+		return NULL;
+	}
+
+	strcat(full_path, "/");
+	strcat(full_path, dms->directory_name);
+	strcat(full_path, "/");
+	strcat(full_path, path_name);
+
+	return full_path;
+}
+
+
+DIR* opendir_in_dms(OBIDMS_p dms, const char* path_name)
+{
+	char* full_path;
+	DIR* directory;
+
+	full_path = get_full_path(dms, path_name);
+	if (full_path == NULL)
+		return NULL;
+
+	directory = opendir(full_path);
+	if (directory == NULL)
+	{
+		obi_set_errno(OBI_UTILS_ERROR);
+		obidebug(1, "\nError opening a directory");
+	}
+
+	free(full_path);
+
+	return directory;
+}
diff --git a/src/obidms.h b/src/obidms.h
index 6ce5f5b..e1ab80d 100644
--- a/src/obidms.h
+++ b/src/obidms.h
@@ -23,6 +23,8 @@
 #include <stdbool.h>
 
 #include "obierrno.h"
+//#include "obidmscolumn.h"
+//#include "obiblob_indexer.h"
 
 
 #define OBIDMS_MAX_NAME (2048) 	    			/**< The maximum length of an OBIDMS name.
@@ -35,21 +37,31 @@
                                 	 	 	 	 */
 #define MAX_NB_OPENED_INDEXERS (1000) 			/**< The maximum number of indexers open at the same time.
                                 	 	 	 	 */
+#define MAX_PATH_LEN 4096						/**< Maximum length for the character string defining a
+ 	 	 	 	 	 	 	 	 	 	 	 	 *	 file or directory path.
+ 	 	 	 	 	 	 	 	 	 	 	 	 */
+
+
+typedef int32_t obiversion_t; 	/**< TODO double
+                                 */
 
 
 struct OBIDMS_column;		// TODO
+typedef struct OBIDMS_column* OBIDMS_column_p;
 
-typedef struct Opened_columns_list {
-	size_t	 		 		nb_opened_columns;
-	struct OBIDMS_column** 	columns;				// TODO allocate array size here
+typedef struct Opened_columns_list {		// TODO Handle the problem linked to columns with the same name + means only one version
+	int	 		 			nb_opened_columns;
+	OBIDMS_column_p		 	columns[MAX_NB_OPENED_COLUMNS];
 } Opened_columns_list_t, *Opened_columns_list_p;
 
 
-struct OBIDMS_avl;		// TODO
+struct OBIDMS_avl_group;		// TODO
+typedef struct OBIDMS_avl_group* OBIDMS_avl_group_p;
+typedef OBIDMS_avl_group_p Obi_indexer_p;
 
 typedef struct Opened_indexers_list {
-	size_t	 		 		nb_opened_indexers;
-	struct OBIDMS_avl** 	indexers;					// TODO indexer but not AVL_group
+	int		 		 		nb_opened_indexers;
+	Obi_indexer_p		    indexers[MAX_NB_OPENED_INDEXERS];
 } Opened_indexers_list_t, *Opened_indexers_list_p;
 
 
@@ -174,4 +186,60 @@ OBIDMS_p obi_dms(const char* dms_name);
 int obi_close_dms(OBIDMS_p dms);
 
 
+// TODO doc
+int obi_dms_is_column_name_in_list(OBIDMS_p dms, const char* column_name);
+
+
+OBIDMS_column_p obi_dms_get_column_from_list(OBIDMS_p dms, const char* column_name, obiversion_t version);
+
+
+void obi_dms_list_column(OBIDMS_p dms, OBIDMS_column_p column);
+
+
+int obi_dms_unlist_column(OBIDMS_p dms, OBIDMS_column_p column);
+
+
+Obi_indexer_p obi_dms_get_indexer_from_list(OBIDMS_p dms, const char* indexer_name);
+
+
+void obi_dms_list_indexer(OBIDMS_p dms, Obi_indexer_p indexer);
+
+
+int obi_dms_unlist_indexer(OBIDMS_p dms, Obi_indexer_p indexer);
+
+
+/**	TODO
+ * @brief Internal function getting the full path of a file or a directory from its
+ *        path relative to a directory file descriptor.
+ *
+ * @warning The returned pointer has to be freed by the caller.
+ *
+ * @param directory_file_descriptor The file descriptor for the directory to which
+ * 									path_name is relative.
+ * @param path_name The path name for the file or directory, relative to directory_file_descriptor.
+ *
+ * @returns A pointer to the full path.
+ * @retval NULL if an error occurred.
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+char* get_full_path(OBIDMS_p dms, const char* path_name);
+
+
+/**
+ * @brief Replacement function for opendirat() : open a directory relative to a directory file descriptor.
+ *
+ * @param directory_file_descriptor The file descriptor for the directory in which the directory should be opened.
+ * @param path_name The path name for the directory to be opened, relative to directory_file_descriptor.
+ *
+ * @returns The file descriptor of the opened directory.
+ * @retval NULL if an error occurred.
+ *
+ * @since June 2015
+ * @author Celine Mercier (celine.mercier@metabarcoding.org)
+ */
+DIR* opendir_in_dms(OBIDMS_p dms, const char* path_name);
+
+
 #endif /* OBIDMS_H_ */
diff --git a/src/obidmscolumn.c b/src/obidmscolumn.c
index c9bcb9d..9479141 100644
--- a/src/obidmscolumn.c
+++ b/src/obidmscolumn.c
@@ -745,8 +745,9 @@ OBIDMS_column_p obi_create_column(OBIDMS_p    dms,
 	close(column_file_descriptor);
 
 	// Add in the list of opened columns
-	*(((dms->opened_columns)->columns)+((dms->opened_columns)->nb_opened_columns)) = new_column;
-	((dms->opened_columns)->nb_opened_columns)++;
+	obi_dms_list_column(dms, new_column);
+
+	// Set counter to 1 // TODO Discuss counters
 	new_column->counter = 1;
 
 	return new_column;
@@ -762,7 +763,6 @@ OBIDMS_column_p obi_open_column(OBIDMS_p dms,
 	char* 						column_file_name;
 	int 						column_file_descriptor;
 	size_t 						header_size;
-	size_t						i;
 
 	column = NULL;
 
@@ -786,14 +786,12 @@ OBIDMS_column_p obi_open_column(OBIDMS_p dms,
 	}
 
 	// Check if the column is already in the list of opened columns
-	for (i=0; i < ((dms->opened_columns)->nb_opened_columns); i++)
+	column = obi_dms_get_column_from_list(dms, column_name, version_number);
+	// If it's found, increment its counter and return it
+	if (column != NULL)
 	{
-		if (!strcmp(((*(((dms->opened_columns)->columns)+i))->header)->name, column_name)
-				&& (((*(((dms->opened_columns)->columns)+i))->header)->version == version_number))
-		{	// Found the column already opened, increase its counter and return the column
-			((*(((dms->opened_columns)->columns)+i))->counter)++;
-			return *(((dms->opened_columns)->columns)+i);
-		}
+		(column->counter)++;
+		return column;
 	}
 
 	// Get the column file name
@@ -892,9 +890,10 @@ OBIDMS_column_p obi_open_column(OBIDMS_p dms,
 
 	close(column_file_descriptor);
 
-	// Add in the list of opened columns and set column counter to 1
-	*(((dms->opened_columns)->columns)+((dms->opened_columns)->nb_opened_columns)) = column;
-	((dms->opened_columns)->nb_opened_columns)++;
+	// Add in the list of opened columns
+	obi_dms_list_column(dms, column);
+
+	// Set counter to 1
 	column->counter = 1;
 
 	return column;
@@ -985,57 +984,35 @@ OBIDMS_column_p obi_clone_column(OBIDMS_p         dms,
 
 int obi_close_column(OBIDMS_column_p column)
 {
-	size_t 				  i;
-	bool   				  close_dir;
-	Opened_columns_list_p columns_list;
+	bool    close_dir;
+	int     ret_val = 0;
 
 	// Truncate the column to the number of lines used if it's not read-only
 	if (column->writable)
-	{
-		if (obi_truncate_column(column) < 0)
-			return -1;
-	}
-
-	columns_list = (column->dms)->opened_columns;
+		ret_val = obi_truncate_column(column);
 
 	(column->counter)--;
 
 	if (column->counter == 0)
 	{
 		// Delete from the list of opened columns
-		for (i=0; i < (columns_list)->nb_opened_columns; i++)
-		{
-			if (!strcmp(((*((columns_list->columns)+i))->header)->name, (column->header)->name)
-					&& (((*((columns_list->columns)+i))->header)->version == (column->header)->version))
-			{	// Found the column. Rearrange list
-				(columns_list->nb_opened_columns)--;
-				(columns_list->columns)[i] = (columns_list->columns)[columns_list->nb_opened_columns];
-			}
-		}
+		if (obi_dms_unlist_column(column->dms, column) < 0)
+			ret_val = -1;
 
 		// Close column directory if it was the last column opened from that directory
-		close_dir = 1;
-		for (i=0; i < (columns_list->nb_opened_columns); i++)
-		{
-			if (!strcmp(((*((columns_list->columns)+i))->header)->name, (column->header)->name))
-			{	// Not the last column from that directory
-				close_dir = 0;
-			}
-		}
+		close_dir = obi_dms_is_column_name_in_list(column->dms, (column->header)->name);
 
 		// If the data type is OBI_STR or OBI_SEQ, the associated indexer is closed
 		if (((column->header)->returned_data_type == OBI_STR) || ((column->header)->returned_data_type == OBI_SEQ))
-		{
 			if (obi_close_indexer(column->indexer) < 0)
-				return -1;
-		}
+				ret_val = -1;
 
 		// Munmap data
 		if (munmap(column->data, (column->header)->data_size) < 0)
 		{
 			obi_set_errno(OBICOL_UNKNOWN_ERROR);
 			obidebug(1, "\nError munmapping column data");
-			return -1;
+			ret_val = -1;
 		}
 
 		// Munmap header
@@ -1043,16 +1020,18 @@ int obi_close_column(OBIDMS_column_p column)
 		{
 			obi_set_errno(OBICOL_UNKNOWN_ERROR);
 			obidebug(1, "\nError munmapping a column header");
-			return -1;
+			ret_val = -1;
 		}
 
+		// Close column directory
 		if (close_dir)
-			obi_close_column_directory(column->column_directory);
+			if (obi_close_column_directory(column->column_directory) < 0)
+				ret_val = -1;
 
 		free(column);
 	}
 
-	return 0;
+	return ret_val;
 }
 
 
diff --git a/src/utils.c b/src/utils.c
index cb287dc..c569141 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -34,55 +34,6 @@
  *
  **********************************************************************/
 
-char* get_full_path(OBIDMS_p dms, const char* path_name)
-{
-	char* full_path;
-
-	full_path = (char*) malloc((MAX_PATH_LEN)*sizeof(char));
-	if (full_path == NULL)
-	{
-		obi_set_errno(OBI_MALLOC_ERROR);
-		obidebug(1, "\nError allocating memory for the char* path to a file or directory");
-		return NULL;
-	}
-
-	if (getcwd(full_path, MAX_PATH_LEN) == NULL)
-	{
-		obi_set_errno(OBI_UTILS_ERROR);
-		obidebug(1, "\nError getting the path to a file or directory");
-		return NULL;
-	}
-
-	strcat(full_path, "/");
-	strcat(full_path, dms->directory_name);
-	strcat(full_path, "/");
-	strcat(full_path, path_name);
-
-	return full_path;
-}
-
-
-DIR* opendir_in_dms(OBIDMS_p dms, const char* path_name)
-{
-	char* full_path;
-	DIR* directory;
-
-	full_path = get_full_path(dms, path_name);
-	if (full_path == NULL)
-		return NULL;
-
-	directory = opendir(full_path);
-	if (directory == NULL)
-	{
-		obi_set_errno(OBI_UTILS_ERROR);
-		obidebug(1, "\nError opening a directory");
-	}
-
-	free(full_path);
-
-	return directory;
-}
-
 
 int count_dir(char *dir)
 {
diff --git a/src/utils.h b/src/utils.h
index 20fddf2..2b4f43a 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -22,44 +22,6 @@
 #define ONE_IF_ZERO(x) (((x)==0)?1:(x))	/**< If x is equal to 0, x takes the value 1.
                                 	   	 */
 
-#define MAX_PATH_LEN 4096				/**< Maximum length for the character string defining a
- 	 	 	 	 	 	 	 	 	 	 *	 file or directory path.
- 	 	 	 	 	 	 	 	 	 	 */
-
-
-/**
- * @brief Internal function getting the full path of a file or a directory from its
- *        path relative to a directory file descriptor.
- *
- * @warning The returned pointer has to be freed by the caller.
- *
- * @param directory_file_descriptor The file descriptor for the directory to which
- * 									path_name is relative.
- * @param path_name The path name for the file or directory, relative to directory_file_descriptor.
- *
- * @returns A pointer to the full path.
- * @retval NULL if an error occurred.
- *
- * @since June 2015
- * @author Celine Mercier (celine.mercier@metabarcoding.org)
- */
-char* get_full_path(OBIDMS_p dms, const char* path_name);
-
-
-/**
- * @brief Replacement function for opendirat() : open a directory relative to a directory file descriptor.
- *
- * @param directory_file_descriptor The file descriptor for the directory in which the directory should be opened.
- * @param path_name The path name for the directory to be opened, relative to directory_file_descriptor.
- *
- * @returns The file descriptor of the opened directory.
- * @retval NULL if an error occurred.
- *
- * @since June 2015
- * @author Celine Mercier (celine.mercier@metabarcoding.org)
- */
-DIR* opendir_in_dms(OBIDMS_p dms, const char* path_name);
-
 
 /*
  * TODO