Status of ClearCase LT Software Change Requests

This file contains descriptions of noteworthy problems found in and not yet resolved in ClearCase LT software running on Windows platforms.

NOTE : The problem descriptions are stored in a change request system keyed to ID numbers. This document lists the numbers, each of which includes a CMBU prefix. The former five-digit number appears in parentheses.

Known Problems in This Release

The following are the known problems in ClearCase LT software.

#CMBU00020310 (#22885) print preview for ClearCase Doctor is broken

The Print Preview menu item was temporarily removed because it was not functioning properly.

#CMBU00021494 (#24216) problems changing ClearCase properties of Visual C++ projects

If you have existing Visual C++ projects in ClearCase LT, then you must manually rename the elements in the VOB that correspond to Visual C++ project file names to have the case-correct names. For example:

cleartool checkout .
cleartool mv foobar FooBar
cleartool mv
...
cleartool checkin .

New projects created in a snapshot view require no such renaming to work properly.

#CMBU00024456 (#27488) Windows 95 power management makes ClearCase LT commands unavailable

When the Windows 95 power management feature activates and switches the disk drive to low-power mode, ClearCase LT shortcut menus (for objects below the level of a view's root directory) and cleartool commands become unavailable.

Workaround : Shut down and restart the machine. Or, to prevent ClearCase LT commands from becoming unavailable on a Windows 95 host, turn off power management:

Choose Start > Settings > Control Panel .

  1. Double-click the Power icon and turn off any power management features in the Power Management dialog box.

#CMBU00025874 (#29026) CCFS changes require restarting ClearCase

If you change the setting of CCFS in the Options tab of the ClearCase Control Panel program, you must shutdown and restart ClearCase before the change takes effect. (You can shutdown and startup ClearCase using the Services Startup tab in the ClearCase Control Panel program.)

#CMBU00026201 (#29379), (#26909), (#30185) global types: differences in command line behavior and GUI behavior

The ClearCase Type Explorer and Properties Browser always display information about local copies of global types, instead of displaying information about the global type.

If the client VOB you are browsing does not contain a local copy of a global type, the ClearCase Type Explorer does not display the global type.

#CMBU00028068 (#31461) diffbl does not work with imported baselines

The cleartool diffbl command, which compares two baselines and shows the differences between them, does not work correctly when one or both of the baselines are imported baselines. An imported baseline is one that you create by importing a labeled set of versions from a VOB.

#CMBU00028214 (#31626) changing activity name breaks link with ClearQuest record

When a ClearCase activity in a ClearQuest-enabled project is linked to a ClearQuest record, the system sets the Name of the ClearCase activity to match the ClearQuest record's ID. This allows users to access the corresponding activity when they are working on a defect by using the current defect number. For example, they can use the command

cleartool setactivity ClearQuest-record-ID

Rational recommends that users not change the name of a ClearCase activity, although ClearCase LT does not prevent that. If users change an activity name, they are no longer able to use the setactivity command as illustrated above.

Note that the Headline field for a ClearCase activity is synchronized with the corresponding field in a ClearQuest record. That is, if users change this field from within either ClearCase LT or ClearQuest, the corresponding field in the ClearQuest record or ClearCase activity is modified as well.

#CMBU00028372 (#31797) removal of branch may result in errors in snapshot view

If a branch is removed from within a snapshot view, any loaded elements from that branch should remain in the snapshot view. However, when trying to list such an element, the program displays the error

cleartool: Error: Pathname is not within a VOB

The error is generated when attempting to list an element if the branched version of the element was previously selected by the snapshot view, but the branch has since been removed. Note that the element still exists in the VOB and the view, it simply cannot be listed by cleartool ls .

#CMBU00029594 (#33174) integration stream property sheets may not show delivered activities

In the Project Explorer, the Activities tab of the baseline and integration stream property sheets does not list the activities that have been delivered to the integration stream and incorporated into the baseline. The Activities tab displays only activities that were created in the integration stream, including integration activities, which ClearCase LT generates during deliver operations.

#CMBU00030053 (#33672) adding large number of files from Windows Explorer fails

If you attempt to add a large number of files to source control from within the Windows Explorer, the operation fails. To add a large number of files to source control, use the cleartool mkelem command instead.

#CMBU00030951 (#34653) defect in MMC taskpads causes Admin Console problems

There is a bug associated with taskpads in the Microsoft Management Console, version 1.1 and 1.2, which causes problems in the ClearCase Administration Console such as the following:

Select the All VOBs or All Views node from the navigation bar of the Administration Console. The program displays the associated taskpad. Now select a VOB or view tag from the taskpad list, and then select Manage storage . After the storage for that node has been successfully displayed, select the MMC "back" navigation arrow to return to and display the previously selected taskpad. Note that the taskpad list is blank.

Workaround: Use either of the following methods to work around the problem:

  • While in taskpad mode, select ViewTaskpad to turn off taskpad mode
  • After navigating to the taskpad with the 'back' arrow, select Refresh from the All VOBs or All Views node.

Note that with MMC 1.1, resizing the console window refreshes the list; resizing has no effect in MMC 1.2

#CMBU00031136 (#34872) deinstalling ClearCase LT may remove Web interface views

By default, views for Web interface users are created under the host data directory for ClearCase LT ( ccase-home-dir \var). If ClearCase LT is deinstalled, the view directories are deleted, but the views remain registered. To avoid leaving entries for nonexistent views in the ClearCase registry, do one of the following:

  • Remove any views created by Web interface users before removing ClearCase LT from a Web server used to provide access to the ClearCase LT Web interface.
  • Use the -view_storage option in the ccweb.conf file to designate some other location for Web interface views.

#CMBU00031803 (#35608) predefined attribute not displayed on property sheet

The cleartool describe command lists predefined attributes for some objects. This output is likely to change at a future release. Specifically, settings that represent UCM information are likely to be removed or replaced with a more abstract representation.

#CMBU00032126 (#35972) modifying properties of deleted view crashes console

If you delete a view while the Properties page of the view is open, and then attempt to modify the view properties, the Administration Console crashes.

#CMBU00032161 (#36013) problem checking in identical .frm files in Visual Basic 6.0

By default, ClearCase LT software does not create a new version of a file that is identical to its immediate predecessor. When you attempt to check in a .frm file that is identical to the checked in version, the integration does not check it in. However, if the .frm file has an associated .frx file, the integration checks in the .frx file as a read-only file. To avoid this problem, set the option to allow identical checkins.

#CMBU00032207 (#36065) extra character appears when merging XML file that contains ASCII key higher than 127

The XML Diff Merge tool displays characters correctly only if they can be represented by a single 8-bit byte. Characters that require two or more bytes, such as UTF-16 characters and some UTF-8 characters, do not display correctly. Although XML Diff Merge accepts XML input in any of four encodings (ASCII, ISO-8859, UTF-8, UTF-16), the merged output file is always encoded in UTF-8. Therefore, we recommend using only ASCII or UTF-8 encodings for XML elements that may be merged.

#CMBU00032286 (#36156) certain file names cause problems in snapshot view

Files with names such as AUX. ext , CON. ext , PRN. ext , or NUL. ext , where ext is any file extension, can be loaded into a snapshot view, but cannot be unloaded from the view or deleted from the system. This makes it impossible to delete parent directories of such files as well. We recommend that you avoid giving files names that are identical to the names assigned to basic system elements.

#CMBU00032491 (#36391) MSWord terminates abruptly when ClearCase LT "SaveAs" initiated

We recommend that you not initiate an Add to Source Control operation from the ClearCase LT menu that appears when you right-click in the SaveAs dialog in MS Word. This may cause your Word application to terminate abruptly, and could possibly cause data loss.

#CMBU00032515 (#36416) missing XML declaration causes other nodes to go missing

When merging XML files, if one contributor version has an XML declaration node, and one or more contributors do not have a declaration node, other nodes between the declaration node and the `root' node can go missing.

To work around this problem, make sure all versions contain an XML declaration node. An example of an XML declaration node is as follows:

<?xml version="1.0"?>

#CMBU00032695 (#36614) opening multiple `nested' ClearQuest forms may cause crash

The UCM/ClearQuest integration does not prevent you from opening a ClearQuest form, then going to the form's UnifiedChangeManagement page, then using the shortcut menu in the change set to open a ClearCase dialog box, and then selecting Activity Properties , which opens a second ClearQuest form.

However, if you follow the above steps, the second ClearQuest form does not function correctly. In particular:

  • The Apply / Revert / Cancel buttons on the form have no text.
  • If you attempt to go to the form's UnifiedChangeManagement page, then dismiss the form, you get the error:

    Unable to load message ID 14090 from resources

After displaying the above error, ClearCase LT crashes.

Therefore, we recommend that you not use the above procedure to open a second ClearQuest form.

#CMBU00032785 (#36712) problems With ClearCase Administration Console if IE4 Not Present

The Microsoft Management Console (MMC), and thus the ClearCase Administration Console, depend on the installation of Internet Explorer (IE) 4.0 or later. In the absence of IE 4, certain ClearCase LT features such as the Web site snapin and the view and VOB taskpads are not available, and the MMC framework in general may behave unpredictably. For example, invoking Help from the console (which is implemented using HTML Help) may cause the console to crash if IE 4 is not available. Additionally, in the absence of IE 4, the MMC menu bar and toolbars may not be available.

#CMBU00033213 (#37203) clearhistory produces extremely small text on Japanese system

The font used for text and captions in the History Browser is 6 point type by default. This point size produces difficult-to-read output in the History Browser on a Japanese language system.

Workaround : To enlarge the font, click View > Options > Display > Fonts and select a larger font.

#CMBU00033224 (#37214) ClearCase LT may not recover from Windows 2000 Hibernate mode

Windows 2000 includes a Hibernate feature that allows the state of the current running system to be saved and restored quickly later on. Active ClearCase LT processes, as well as processes that have the ClearCase Network Provider loaded, may have TCP connections to servers on remote machines; such connections are likely to be closed by the servers during the time the system is in Hibernate mode. Therefore, the client ClearCase LT applications are likely to return errors when a user attempts to use them after the machine has been brought back from Hibernate mode.

#CMBU00033367 (#37371) delivery of selected activity does not detect directory dependency across activities

If you create a new element in one activity (for example, A), while the directory containing the element is checked out to a different activity (for example, B), you have created an implicit dependency of A on B. When selectively delivering activity A, you must also include activity B. Otherwise deliver reports the error, DBID not found .

#CMBU00033455 (#37464) pre-checkin trigger causes problem in Visual Basic projects

In Visual Basic when you attempt to add a project to ClearCase by clicking Tools > ClearCase > Add Files to ClearCase , the operation fails if the VOB in which the Visual Basic project resides has a trigger that requires users to enter a comment when checking in files. The Visual Basic IDE does not supply the comment that you enter in the Add to Source Control dialog box to the trigger.

To work around this problem, use ClearCase Explorer to add the project to source control. After you add the project to source control, checkin and checkout operations complete successfully from within the Visual Basic IDE.

#CMBU00034080 (#38169) Date/Time settings change when switching tabs

Due to a problem in earlier versions of Windows, the Date/Time control used in the Settings page of the Job Properties sheet may sometimes toggle inappropriately from PM to AM. The Job Properties sheet is part of the new Job Scheduler available through the ClearCase Administration Console .

If the current time is in the PM and the user types in a new time, rather than using the arrow keys on the keyboard or the spin control on the Date/Time control to set the time, the AM/PM field switches to AM.

This problem appears to be fixed in the latest version of Internet Explorer 5.0.

#CMBU00034241 (#38345) cannot checkin to non-UCM VOB from UCM view if ClearQuest enabled

If, in a UCM view, you check out or check in an element from a VOB which is not a UCM component, you should not have to select an activity, because that operation is not captured in a change set.

However, if you are in a view which is in a ClearQuest-enabled project, both the Check Out dialog box and the Check In dialog box force you to select an activity even though one is not really required.

Workaround : Simply select the activity, it will be ignored.

#CMBU00034354 (#38464) no reporting of ClearQuest script error text

Using the UCM-ClearQuest integration, you can customize the Check Before Deliver ClearQuest Visual Basic policy script. However, if the script as customized contains an error that causes the Visual Basic interpreter to display an error exception, the Deliver dialog box reports this error like this:

An error occurred during the deliver.
Unexpected error in deliver.

It does not report the actual error exception text which would enable the user to diagnose the problem script

Workaround : To see the error exception text, use the cleartool deliver command.

#CMBU00034355 (#38465) must kill ClearQuest server to see schema upgrade

Using the UCM/ClearQuest integration, if you upgrade a ClearQuest user database to a new schema revision, in order to see the change on a client machine which was connected to that user database, you must do the following on the client machine:

On Windows NT or Windows 2000:

Open the Task Manager and go to the Processes tab page

  1. From the list, select CQINTS~2.EXE or CQINTSVR11.EXE
  2. Click End Process

On Windows 98:

Type CTRL+ALT+DELETE

  1. In the list that opens, select CQINTSVR11
  2. Click End Task

#CMBU00034481 (#38606) changes to UCMCustomQuery1 do not appear in dialog box

When using the UCM/ClearQuest integration, the list of records displayed in the dropdown list on the Add To Source , Check Out and Check In dialog boxes is generated by running the UCMCustomQuery1 query, which can be customized. (Note that in order to see the effect of your changes, you must use the File > Save menu item to save the query edits.)

However, if you copied the Public Queries UCMCustomQuery1 query into your Personal Queries folder and edited it there, the changes are not immediately seen. To see your changes, you must stop the integration server process:

On Windows NT or Windows 2000:

Open the Task Manager and go to the Processes tab page

  1. From the list, select CQINTS~2.EXE or CQINTSVR11.EXE
  2. Click End Process

On Windows 98:

Type CTRL+ALT+DELETE

  1. In the list that opens, select CQINTSVR11
  2. Click End Task

After stopping the process on your computer, open the dialog box again. Further edits to /PersonalQueries/UCMCustomQuery1 show up automatically without having to shut down the process again.

#CMBU00034719 (#38869) Refresh button may vanish in ClearCase Administration Console

While displaying a view private file in the ClearCase Administrator's or Host Console, resizing its column headers or displaying the shortcut menu causes the Refresh toolbar button to be hidden. If this happens, you can access the Refresh action by using the Action menu pull-down, or from the shortcut menu of the view private file's display.

#CMBU00035155 (#39334) confusing error message when using PowerBuilder Integration

When using the PowerBuilder integration with ClearCase LT software, if you select an object from the public directory and click Source > Register , the integration displays a dialog box where you enter the name of the .PBL library. If you enter the name of a .PBL library that does not exist in the archive directory, the integration creates a new .PBL library and adds it to source control in the archive directory. If you attempt to check out the same object from the public directory by clicking Source > Check Out , and you specify a different .PBL name, the integration fails with an "error5" message. To work around this problem, be sure to enter the exact name of the target .PBL when you check out an object.

#CMBU00035331 canceling an uncheckout confirm window hangs ClearCase/FrameMaker integration

There is a known error that occurs when canceling an uncheckout confirmation dialog. It causes Adobe FrameMaker to hang.

#CMBU00039678 FRX file not checked out when part of Visual Basic Group

In a Visual Basic version 6.0 project that is part of a Visual Basic Group, when you check out a .FRM file (with a .FRX file), ClearCase LT does not check out the associated .FRX file automatically. This behavior may cause synchronization problems. When working with a Visual Basic 6.0 project that is part of a Visual Basic Group, be sure to check out both the .FRM and .FRX files.

#CMBU00040256 error message when opening Visual Basic 6.0 project

When you open a Visual Basic 6.0 project that is checked in, the integration displays the following error message: "Failed to update project location information in the host application". The integration displays this message because the Visual Basic project file is not checked out and the project location information cannot be updated. To avoid this message, check out the project file and then open the project. If you choose to check out the project file in advance, you may safely ignore this message.

#CMBU00042553 Diff Merge tool does not display multibyte characters correctly

The Diff Merge tool may not display multibyte characters correctly.

Workaround:

On the Tools menu in Diff Merge, open the Options dialog box .

  1. Click Change .
  2. Change the font to one that displays multibyte characters correctly on your machine.

#CMBU00042778 cleartool commands use one date format

The output of most cleartool commands that display date information uses an invariant format that ignores regional standards.

#CMBU00042408 clearexport_cvs -A must have -r specified

When running clearexport_cvs , the -A option has no effect if -r has not been specified also.

#CMBU00044461 Visual C++ Addin toolbar altered by move to Windows 2000

If you install Windows 2000 on a machine that currently runs Windows NT with the ClearCase LT-Visual Studio integration, and you re-install ClearCase LT software, the Visual C++ 6.0 Addin toolbar for the ClearCase LT integration contains five Version Tree buttons. All five buttons start the Version Tree Browser. To correct the problem, remove the ClearCase LT toolbar and then re-add it:

Click Tools > Customize and select the Add-Ins tab.

  1. Uncheck ClearCase LT on the list and close the dialog box.
  2. Click Tools > Customize a nd select the Add-Ins tab.
  3. Check ClearCase LT on the list and close the dialog box.

#CMBU00044722 using ClearCase LT Web Interface, problem overriding primary group

When the ClearCase LT Web server running on Windows logs in a client, it sets the primary group to the designated primary group in the client user's domain account. In ClearCase LT software, you cannot override this group setting. As a result, sites that use domain mapping to allow user accounts in multiple domains to share VOBs cannot access those VOBs through the ClearCase LT Web Interface.

#CMBU00044756 changing name of ClearQuest record type causes error

In the UCM-ClearQuest integration, if you change the name of the ClearQuest record type after activities have been linked to ClearQuest records of that record type, the integration displays an error message when you try to set one of those activities in a view. To change the name of a record type, do so before any activities are linked to records of that record type.

#CMBU00044858 admin console shows empty logs

The Server Logs node of the Clearcase Administration Console may display the names of several logfiles that never have any content on a ClearCase LT Server. These logfiles include:

msadm
promote
rgy_backup
shipping
sync_export
sync_import
ws_helper

#CMBU00045827 mounting VOB with read-only options allows everyone to write inside

On Windows NT, mounting VOBs with the read-only option ( ro ) has no effect.

#CMBU00046148 eclipsed files in ClearCase Explorer

If you rename or delete an eclipsed file, the operation is performed only on the view private object that is eclipsing the ClearCase element.

The exception to this is when the view private file is being edited in Microsoft Word. Word maintains a lock on the file which makes it impossible for any other program to touch or operate on the file

Workaround: Close the file in Word, or use the ClearCase integration with Word.

#CMBU00046610 removal of ClearCase LT Icon

You can install ClearCase LT software as a point product on the same machine on which you install a Rational Suite. If you later uninstall the Rational Suite, the icon for ClearCase LT software is removed from the desktop, but the product is not uninstalled. The ClearCase LT program is left on the computer as is its reference in Start > Programs . The icon should not be removed, because ClearCase LT software must be uninstalled separately. As a workaround, you can manually put the icon for the ClearCase LT Explorer on the desktop.

#CMBU00046883 source output window no longer displays ClearCase status messages

To enable logging text to display inside an IDE, the user must set the registry key HKEY_CURRENT_USER\Software\Atria\ClearCase\CurrentVersion\SCC\DebugTrace = 1 (or = 3 for additional logging to a file).

#CMBU00047773 user cannot remove UCM permanently from ClearCase Explorer

The UCM shortcut pane always appears in the ClearCase Explorer. You cannot set the Explorer to not display UCM. If you remove all shortcuts from the UCM section, UCM disappears. However, the system does not save the configuration. After you close the Explorer and reopen it, the UCM shortcut pane appears again.

#CMBU00048303 lsclients command no longer shows if release is patched

Patch information for ClearCase releases might not be correctly displayed by cleartool lsclients .

Workaround: Use cleartool -ver .

#CMBU00050011 ClearQuest security model displays ClearCase error message

For users who belong to a user group that is not allowed to see the ClearQuest record, the following error message appears when they specify the record while performing an Add to Source Control , Checkout , or Checkin New operation from a ClearCase GUI:

Error! Execution of a hook failure during the action Submit.
It was the ACTION_COMMIT hook attached to the BaseCMActivity `cqms0000111".
The reason for the failure was:
IDispatch error #14094
UCM_Project 33554485 does not exist or has already been deleted.

Problems Fixed in ClearCase LT Version 2001A.04.00

Table 1 lists significant problems in previous ClearCase LT releases that are fixed in this release.

Table 1 ClearCase LT Problems Fixed in This Release

Problem Number

Description

#CMBU00017656

error opening config_spec, broken pipe during view startup

#CMBU00022765

(#25622)evaluation license not removed unless ClearCase is removed

#CMBU00042511

extended ASCII characters in comment input filenames not recognized

#CMBU00045520

a Start menu item unsupported

#CMBU00045837

Attache 4.1 helper causes edcs, find, findmerge, update commands to fail

#CMBU00046916

server name input field may be too short

#CMBU00048023

unreserved checkout preference cannot be overidden by checkout GUI

#CMGU00047130

pbimport.exe (built for release) produces application error when versioning PBLs

#CMBU00049152

restrictions on node size in the XML Parser removed

Disposition of Previously Reported Problems

Table 2 lists the status of problems reported in previous releases.

Table 2 Disposition of Problems in Previous ClearCase Releases

Problem Number

Status

Description

#CMBU00015494

No Plan to Fix

(#17463) the MVFS cannot be shut down

#CMBU00017662

No Plan to Fix

(#19870) add to source control fails when using UNC names

#CMBU00019049

No Plan to Fix

(#21459) opening ForeHelp backup file in a view fails

#CMBU00022771

Not a Bug

(#25628) view profile wizard fails if there is no existing local copy of a global label type

#CMBU00022877

Irreproducible Bug

(#25742) problem opening saved ClearCase Doctor file

#CMBU00023706

Moved to Administering ClearCase

(#26665) avoid `:' usage in an environment that requires UNIX/Windows interoperation

#CMBU00024917

Fixed in 4.1

(#27994) two licenses per user required under some conditions

#CMBU00026345

Fixed in 4.1

(#29545) interoperability issues if NFS not running on system

#CMBU00028939

Option removed

(#32429) cannot use clearimport -nsetevent on datafile created by clearexport_ccase

#CMBU00029384

Fixed in 4.0

(#32929) creating multiple baselines in same day requires name change

#CMBU00029402

No Plan to Fix

(#32954) conflict between Visual J++ toolbar and Exceed/xcleartrack

#CMBU00029537

Fixed in 4.1

(#33106) need to reselect contributors to do compare of same XML files

#CMBU00031171

Moved to ClearCase Reference Manual

(#34909) rebase silently resets activity in a view

 

#CMBU00031654

Fixed in 4.1

(#35440) XML Diff Merge tool translates entities on output

#CMBU00032016

Fixed in 4.1

(#35849) ambiguous error when submitting a new ClearQuest record

#CMBU00032126

NPTF

(#35972) modifying properties of deleted view crashes console

#CMBU00032167

Fixed in patch 6.2.0.1 from Hummingbird

(#36021) using Maestro 6.1.1.1/6.1.1.2 to access exported UNIX root (/) file system crashes Windows client system

 

#CMBU00032514

Fixed in 4.1

(#36415) some conflict situations cause XML Diff Merge to crash

#CMBU00032736

Fixed in 4.0

(#36658) XML Diff Merge tool tips on contributor buttons wrong

#CMBU00032785

Fixed in 4.0

(#36712) problems With ClearCase Administration Console if IE4 Not Present

#CMBU000 33949

Fixed in 4.0

(#38023) rebase -cancel doesn't reset config spec

#CMBU00034124

Fixed in 4.0

(#38217) describe/lstype/lshistory of an eclipsing ordinary type incorrectly forwards to global type

#CMBU00034385

Fixed in 4.1

(#38501) View Creation Wizard displays `switching project context" error

#CMBU00034551

Fixed in 4.0

(#38684) cannot configure server storage with Configuration Wizard

#CMBU00034608

Fixed in 4.1

(#38747) Compare/Merge as Text sometimes fails to launch on long file names

#CMBU00034652

Fixed in 4.1

(#38794) cannot view Properties of Version for multiple versions at once

#CMBU00034721

Fixed in 4.1

(#38871) problems using UCM/ClearQuest integration with SQL Server or Oracle database

#CMBU00034898

Fixed in 4.1

(#39058) ClearCase Doctor falsely reports user "Home Directory Not Accessible"

#CMBU00034920

Fixed in 4.1

(#39081) rebase error falsely implies corrupted VOB or view

 

#CMBU00038442

Fixed as #CMBU00030727

(#37817) findmerge and Find Wizard cannot traverse symlinks in snapshot views

#CMBU00038668

Fixed as #CMBU00033949

(#37678) canceled rebase causes incorrect view behavior

#CMBU00042838

Fixed in 4.1

XML Diff Merge generates complex display of differences

#CMBU00044770

Fixed in 4.1

Attache Helper memory corrupted when reading large directory

#CMBU00045368

Patched in 4.1

the contributors to the Word merge operation are reversed