I have many error-date.log files taking up a large amount of space, which is causing space issues on my SEPM. Can I delete these? What is the purpose of these?

They're located in C:\Program Files\Symantec\Symantec Endpoint Protection Manager\apache\logs

Any help is appreciated!

SEPM 12.1 RU3

yes you can safely delete those..

What do they do and why are they there in the first place? The majority of the files are 250Mb+ in size??!!

they generate only error logs

Apache Web Server Logs

Hello,

By default Apache Server generates only Error logs and stored in C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\apache\logs

If you have enabled access log or communication log and you have many clients then there is a possiblity that Logs folder is huge in size.

The following articles may help. 

It exaplains how to enable Apache access logging.... it sounds like that may be what is happening on that SEPM.  Just reverse the steps to disable it:

Apache Web Server Logs

http://www.symantec.com/docs/TECH94290 

Symantec Endpoint Protection Manager 12.1 Communication Troubleshooting

http://www.symantec.com/docs/TECH160964

Enabling and viewing the Access log to check whether the client connects to the management server

You can view the Apache HTTP server Access log on the management server to check whether the client connects to the management server. If the client connects, the client's connection problem is probably not a network issue. Network issues include the firewall blocking access, or networks not connecting to each other. You must first enable the Apache HTTP server Access log before you can view the log.

Note: Disable the log after you view it because the log uses unnecessary CPU resources and hard disk space.

To enable the Apache HTTP server Access log:

1.In a text editor, open the file

C:\Program Files\Symantec\Symantec Endpoint Protection Manager\apache\conf\httpd.conf.

2.In the httpd.conf file, remove the hash mark (#) from the following text string and then save the file:

#CustomLog "logs/access.log" combined

3.Using services.msc, restart the Symantec Endpoint Protection Manager Webserver service (Apache)

Click "Yes" to also restart the SEPM service

To view the Apache HTTP server Access log:

1.On the management server, open

C:\Program Files\Symantec\Symantec Endpoint Protection Manager\apache\access.log

2.Look for a client computer's IP address or host name, which indicates that clients connect to the Apache HTTP server.

3.Disable the Apache HTTP server Access log when done.

Secondly, check this Thread with similar issue:

https://www-secure.symantec.com/connect/forums/huge-log-files

Hope that helps!!

This started happening when I changed the logging required by the GUP monitor. I bet this is what is causing this!

Delete those and turnoff the logging , use it only when required.

I deleted them but it is required to get accurate numbers from the GUP monitor

This the problem with enabling the logging for the GUP monitor. You can manually delete these or I have a batch file which will do it automatically. Contact me via PM if you want it.

Otherwise, you do not need to enable the logging and just use it make sure your GUPs are online. The logging of content downloads is nice but may cause a disk space problem, as you've already seen.