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+---
+layout: article
+title: CAS Tables
+description: Dealing with CAS (in-memory) Tables in Data Controller
+og_image:  /img/SAS-Viya-and-CAS-300x249.png
+---
+
+!!! warning
+    Work in Progress!
+
+# CAS Tables
+
+CAS Tables require special consideration in Data Controller with regards to the following topics:
+
+ - System Account
+ - Loading
+ - Unloading
+ - Special Variables
+
+## System Account
+
+Despite having a shared SYSUSERID, the SPRE session will (by default) authenticate using the logged-in user credentials.  To get around this, it is necessary to set up the CAS connection in the autoexec - ie, before the user takes over the session.  The code snippet will be:
+
+```sas
+%let _CASHOST_ = <your-host>;
+
+%let _CASPORT_ = 5570;
+
+cas dcsession authdomain="<your-domain>" sessopts=(caslib=casuser);
+```
+
+The credentials need to be first placed in the viya credentials service as described [here](https://go.documentation.sas.com/doc/en/pgmsascdc/v_073/casref/n0z3r80fjqpobvn1lvegno9gefni.htm#p11ynzjbz96oq1n17rgt2utv6swj).
+
+Another approach can be to use the `AUTHINFO="authentication-file" option, as described [here](https://go.documentation.sas.com/doc/en/pgmsascdc/v_073/casref/n0z3r80fjqpobvn1lvegno9gefni.htm#n174yddgn85756n1v5q4yb881xa0).
+
+Note that since the CAS connection is using a shared account, the CASUSER library is never shown in the DC interface.
+
+## Loading
+
+It can happen that a CAS table is configured in Data Controller but not loaded into memory. In this case, when a user selects the table, it will be automatically loaded.
+
+## Unloading
+
+After an approval, the in-memory version of the CAS Table will be updated.  To apply this to the underlying file on disk, the following code must be executed (eg in a POST APPROVE HOOK):
+
+```sas
+proc casutil;
+   save casdata="mytable" incaslib="mycaslib"
+        casout="mytable" outcaslib="mycaslib"
+        replace;
+quit;
+```
+
+## Special Variables
+
+Processing of data in Data Controller is performed in SPRE with SAS datasets - and as such, it is not possible to process character variables longer than 32k or other CAS specific data types.
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diff --git a/mkdocs.yml b/mkdocs.yml
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--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -39,6 +39,7 @@ nav:
     - MPE_XLMAP_INFO: tables/mpe_xlmap_info.md
     - MPE_XLMAP_RULES: tables/mpe_xlmap_rules.md
 - Configuration:
+    - CAS Tables: cas-tables.md
     - Column Level Security: column-level-security.md
     - Dates / Datetimes: dcc-dates.md
     - Dynamic Cell Dropdown: dynamic-cell-dropdown.md