If you want Open/Client v15.7 for Windows OS:
It looks like v15.7 PC Client is still available for both 32-bit & 64-bit (sp100, sp122, sp130, sp135, and sp60)
note: I understand that there was a base-release of “Sybase ASE 15.7 Refresh PC-Client ” (pre-sp100) that came with the ASE 15.7 ESD#1 install media (under ‘Installations and Upgrades’).
Below are steps to the updated PC client (under "Support Packages and Patches").
You would select 'Windows Server on IA32 32bit' as it does contain both 32-bit and 64-bit client installs.
Here is a step-by-step to "PC Client”
SAP Support portal @ https://support.sap.com/home.html?url_id=text-SMPHomepage-newsupportportal
select "SAP Software Download Center"
select "Support Packages and Patches"
select "A–Z Index" select "A"
select 'SAP ADAPTIVE SERVER ENTERPRISE'
select 'SYBASE ASE 15.7'
select 'SYBASE PC CLIENT 15.7'
select 'Windows Server on IA32 32bit'
You should see at bottom of page a refreshed list of PC Client versions (items) that can be downloaded...
For example,
I select [] [] Object information ZIP PCCLIENT1570135_0-20011197.ZIP EBF 24959: 15.7 SP135 0 Info 1769004 11.07.2015 ' <<< this includes both 32-bit/64-bit PC Client.
If you select the 'Info' item to the right, another page pops up... you select the note 2191031 (SYBASE PC CLIENT 15.7).
And that opens a new window listing the SAP NOTE 2191031 – SYBASE PC Client 15.7 Release Notes Information
This SAP Note 2013184 contains the README, File list, Bug List files for the selected patch (‘EBF24959_NT_I386_README.htm’, ‘EBF24959_NT_I386_Buglist.txt’, and ‘EBF24959_NT_I386_Filelist.txt’)
Otherwise, you would use Bret's steps to navigate to SDK (for Windows) and run the "Custom" install option to complete the Open/Client component installation.
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If you want Open/Client v15.7 or v16.0 for UNIX:
Option#1: See KBAs:
2252628 How to Download the SDK for SAP ASE
2093510 How to Download Free SDK for SAP ASE [Windows, Linux, Unix]
https://service.sap.com/sap/support/notes/2252628
https://service.sap.com/sap/support/notes/2093510
Option#2: Follow Bret's steps to navigate to SDK and run the "Custom" install option to complete the Open/Client component installation.
Lastly, additional information for SDK or Open/Client can be addressed in the following:
SAP Community Network -(Client and drivers interoperability with ASE versions):
http://wiki.scn.sap.com/wiki/display/SYBCON/SAP+Connectivityhttp://wiki.scn.sap.com/wiki/display/SYBCON/Client+and+drivers+interoperability+with+ASE+versionshttp://wiki.scn.sap.com/wiki/display/HOME/Software+Developer+Kit+for+ASE+driver+versions+for+Windows
Regards, -Michael